Category Archives: Cloud seeding

Cloud Seeding and the Journal Barriers to Faulty Claims: Closing the Gaps

This manuscript had a close call in being accepted into the American Meteorological Society’s  Bull. Amer. Meteor. Soc. in 1998-1999.  The key reviewer that I had to satisfy (according to journal Editor  I. Abrams)  insisted that I make it clear that the cloud seeding experimenters in Colorado  and Israel did the “best they could with the tools available at that time”, paraphrasing here.

I couldn’t do it.

I had personal experience with the leaders of both those benchmark experiments; one was intransigent regarding new facts that upset a key claim he repeatedly made about the height of cloud tops in the Rockies during storms, and the other leader denied me access  to his radar to observe cloud top heights (and thus obtain temperatures).  I went to Israel suspecting that his many papers on the clouds of Israel were in major error.  (They were later proved to be in major error  on several occasions over the following 20 years.)

So, how could I agree with the key, “Reviewer B” stating that those experimenters did the best they could?  I might have “got in” by doing that.  Both cloud seeding leaders caused their respective country’s millions of dollars in wasted cloud seeding efforts.

An updated  “Gaps” manuscript was rejected a second time (!) in 2017 or so by the editor of the weather modification/cloud seeding issue of “Advances in Meteorology”, L. Xue, as “not the kind of paper we were looking for.”  Perhaps, though, it’s the kind of article YOU were looking for:

2017 Gaps-revised following comment

Review and Enhancement of “Literature Review and Scientific Synthesis on the Efficacy of Orographic Cloud Seeding”


Dr. Reynolds, the sole author of this monumental review I critique  has done a masterful job of surveying an enormous amount of cloud seeding literature in his “draft” report to his former employer, the Bureau of Reclamation.  The BOR was  the primary sponsor of cloud seeding programs throughout the West in the 1960s to the 1980s.  However, as was also seen in a recent review of the 2009 Springer book,  “Impacts of Aerosols on Precipitation,” such a task appears to be too much despite Reynold’s valiant efforts to “get it right.”   Reynold’s discussions of the benchmark randomized experiments in Colorado that led to the nation’s largest, most costly randomized orographic cloud seeding experiments, the Colorado River Basin Pilot Project, is an example of the problem of having too much to review and not enough time to scrutinize the details of so much literature.

Reynold’s review is well-written, most of the necessary citations are in it that help the reader to understand the topic.    That is,  except for those elements in his review that I am perhaps, a little too familiar with and I feel must be addressed in this VERY belated review of his 2015 draft report.

“Too familiar?”

That’s what happens to someone who has spent thousands of volunteer hours (crackpot alert!) rectifying faulty cloud seeding and cloud claims in peer-reviewed journal articles because he felt, “Someone has to do something about this!” (Second crackpot alert, with possible megalomaniacal implications).   I was employed as a weather forecaster for the Colorado River Basin Pilot Project for all of its five winter operating seasons, 1970/71 through 1974/75.  No one can know about that project and the faulty literature it was based on more than me.  I came in naive and idealistic about the scientific literature on cloud seeding;  I didn’t leave that way

I was not asked to review Reynold’s 2015  review before he posted his report to the BOR  online as a “draft,” the status it retains as of today.   I contacted Dr. Reynolds recently and informed him that I had a few comments on and corrections to his review.  He replied that he was not interested in correcting his review or making changes at this time.  This seemed odd to me, so here we are.

Also, in the spirit of “author disclosure,” I should mention that Dr. Reynolds was also an informal reviewer of my manuscript co-authored with Prof. Dave Schultz, Manchester U., on the history of the BOR-funded Colorado River Basin Project.  It was recently rejected by the J. Appl. Meteor.  due to length.  We are in the process of seeing where that manuscript can be trimmed down without losing  important parts of the story.

The comments pn Reynold’s review would have likely been unnecessary had I reviewed it beforehand, or if Dr. Reynolds  wished to consider my comments and corrections today.    I was well known to Dr. Reynolds as an expert on clouds, cloud seeding, and the weather  in Colorado and Israel ;  he had previously cited my work his 1988 article in the Bull. Amer. Meteor. Soc.   With Professor Peter V.  Hobbs in tow, I dissected those landmark experiments in Colorado and Israel and showed they were, as Foster and Huber (1997) described faulty science,  “scientific mirages.”  They were “low-hanging fruit” that poor peer reviews of manuscripts had let in, mostly, appearing Amer. Meteor. Soc. journals.  It didn’t take a genius to unravel them.

Dr. Reynold’s comprehensive  review can be found here.  It is too long to be a blog post here that includes my embedded comments.  Since I am only commenting on certain sections,  I have extracted only those portions of Reynold’s review where I have made comments.  It may be that only those familiar with this topic, orographic cloud seeding, will be interested, but, oh, well….  It has to be done even if for only ONE person!

My goal is to be objective and not short change Reynolds’ work on what is really an astounding effort.  It would take me two lifetimes to do what Dr. Reynolds has done.

I also believe Dr. Reynold’s made a great effort to be objective in discussing a topic that almost always brings controversy.  The literature in this field is filled with pro-seeding partisans that have often edited results so that cloud seeding has been presented with a happier face than it should have been.  After all, no one got a job saying cloud seeding doesn’t work (is not viable for producing worthwhile amounts of water.)

Considering his background in the cloud seeding arena, Reynolds final conclusion, copied below, must be considered an example of high integrity and his conclusion is one that this author fully agrees as of this date:

“5.3.2 Final Conclusion 

Based on both the historical evidence and the last decade of research, it is reasonable to conclude that artificial enhancement of winter snowpack over mountain barriers is possible. It is very difficult to quantify the seasonal increases to be expected both in snowpack and subsequent spring runoff. This is because each target area has to be investigated as to the meteorology of the winter clouds and their seedability, and the engineering aspects of effectively seeding the clouds to maximize increases. Winter orographic cloud seeding should thus continue to be supported both from the scientific and operational community working together to further the science and operational outcomes. It must be stated however, that as of yet, no rigorous scientific study conducted as a randomized confirmatory seeding experiment with pre-defined primary response variables and requiring an established threshold of statistical significance has demonstrated that seeding winter orographic clouds increases snowfall. As such, the “proof” the scientific community has been seeking for many decades is still not in hand. “

================THE REVIEW=================

My comments, corrections and question on Dr. Reynolds review begins below and are in a red font.   Highly relevant citations are missing  and there are citations in the Reynold’s references that do not appear in the text.  The missing ones, annotated with a “u” ,  have been added at the end of this review.

The portions of Reynold’s review that I examined begins here:


1.0 Introduction 

1.1. Introduction to Winter Orographic Cloud Seeding In its most basic form, artificial seeding of clouds for precipitation enhancement can be divided into two broad categories: 1 – cloud seeding to enhance rainfall i.e. summer convection, 2 – winter orographic cloud seeding to enhance snowfall. The scope of this paper is only concerned with the latter. Winter orographic cloud seeding occurs when very small particles, typically silver iodide, are introduced into a cloud which is below freezing. The cloud moisture collects onto the small particles, freezing the moisture into tiny ice crystals which continue to grow until they become too heavy to remain in the cloud and then fall out as precipitation (typically snow). This process can happen rapidly on the windward slopes of mountains allowing the snow to fall near the crest of the mountain which causes a local enhancement to the amount of precipitation that would have fallen naturally (Figure 1.1).

The situation is complicated if the natural crystals are becoming rimed and due to riming, fall more quickly.  Adding more ice crystals via cloud seeding may result in raising their trajectories by reducing riming and the snow may not be increased snow where it is wanted, or will evaporate in the descending, drying  air on the lee side.  The schematic below would be valid for naturally non-precipitating clouds.  

The properties of clouds that don’t naturally precipitate vary with location.  Maritime clouds along the west coasts of continents generally can precipitate without ice.  Farther inland, where the clouds become impacted by natural and anthropogenic aerosols, ice is generally required for precipitation and may not develop until cloud tops are cooler than about -12°C.  These latter non-precipitating clouds make viable seeding targets.

Figure 1.1 – Simple model of winter orographic cloud seeding. 1 – Introduction of seeding material, 2 forced ascent due to topography, 3 – enhanced precipitation falling out of cloud. 

1.3 Relevance and Need for a Reassessment of the Role of Winter Orographic Cloud Seeding to Enhance Water Supplies in the West 

Weather modification is most commonly conducted through “cloud seeding,” the introduction of chemical agents with the intent of affecting precipitation processes. A number of academic and private entities exist that offer services to states and local governments with the aim of increasing water supplies through inducing precipitation volumes above which would occur naturally. From the 1960s through the 1980s, Reclamation was involved in a variety of weather modification initiatives in the west under Project Skywater. This project included the Colorado River Basin Pilot Project, the High Plains Experiment (summer only), and the Sierra Cooperative Pilot Project. Project Skywater was terminated in 1988, but Reclamation continued to be involved with weather modification efforts. Reclamation participated in the development of the California Department of Water Resource’s design and conduct of the Oroville Reservoir Runoff Enhancement Project from 1988 until 1994. Reclamation also supported other efforts through the mid-2000s, including the Weather Damage Modification Program. 

Based upon scientific literature through 2006 and discussions with experts in the field, the efficacy of weather modification appears to be unsettled. In 2003, the National Research Council (NRC) report “Critical Issues in Weather Modification Research” (NRC 2003), concluded that “there is still no convincing scientific proof of the efficacy of intentional weather modification efforts”. The NRC goes on to state that new technology allows for potential new research to help understand the process of precipitation and if weather modification is a viable means to increase water supplies. 

The NRC 2003 review of cloud seeding cited above  did not measure up to the one the NRC published in 1973.  I reviewed NRC 2003.  If anyone cares, can be found here:         

 A Critical Review of NRC 2003 Critical issues in weather modification NATIONAL ACADEMIES PRESS

As seems to be typical of reviews, there was just too much literature to review for the scientists involved, and also likely, not a top priority for those assigned to this task having other research on their plates.   Prof. Hobbs, with my acquiescence, helped compromise this review by declining an offer by Prof. Garstang, chair of the review committee, to review before it was published, a huge mistake.  Garstang admonished  Peter to not to comment on it AFTER it came out.  But that’s exactly what Peter told me we would do if needed.  I nodded and went back to my desk.  He said we would have “more impact” by doing that.  I hope you appreciate getting stories from behind the scenes.

In 2002-2003, Reclamation funded, through earmarks, weather modification studies in the states of Nevada, Utah, California, North Dakota, and Texas. The studies did not provide convincing scientific evidence that weather modification reliably generates additional water. However, there are a number of studies, including from within Reclamation (Hunter 2004 – cited within LBAO (Lahontan Basin Area Office) EA discussed later), that indicate that cloud seeding can significantly increase precipitation amounts for targeted locations. 

Statement on the Application of Winter Orographic Cloud Seeding For Water Supply and Energy Production 

In 2005, Reclamation primarily stopped involvement in weather modification efforts at the program level. As identified within Q&As developed by the Research and Development Office explaining Reclamations abandonment of the practice: 

•Weather modification is not an operational function of Reclamation.

•In a letter dated December 13, 2005, sent to then-Texas Senator Kay Bailey Hutchison(R), the White House Office of Science and Technology Policy (OSTP) said there aresignificant concerns about liability and legal ramifications of weather modification,including whether weather modification can be demonstrated to actually be effective.

Since 2006, continuing drought conditions, and a strong interest amongst some Reclamation stakeholders, Reclamation engaged in two research projects related to weather modification in support of cold-season snowfall enhancement. 

•In 2010 the Mid-Pacific Region’s LBAO finalized an Environmental Assessment (LBAOEA) proposing to provide $1.35 million from Reclamation’s Desert Terminal LakesProgram to the Desert Research Institute (DRI) for a cloud seeding project in the WalkerRiver Basin.

•At a March 12, 2014 meeting of the Upper Colorado River Commission, weather modification was specifically identified as one of three activities that the Upper Basin states propose to include within their drought contingency plans. The Upper Basin states asked that Reclamation provide partial support for Wyoming’s eighth year (2014) of an ongoing weather modification study / program being conducted with the National Center for Atmospheric Research (NCAR). This request resulted in Reclamation’s Upper Colorado Region obligating $200,000 to the State of Wyoming for weather modification research and development efforts conducted by NCAR, with these monies obligated through an amendment to an existing cooperative agreement between Reclamation R&D and Universities Corporation for Atmospheric Research.

The Upper Basin states have noted that state and private entities in Colorado and Utah spend over $1M and $500,000 respectively on weather modification, and estimate efficacy between 6% and 20%. At the low end, the Upper Basin states identify that a benefit of 6% is inexpensive water within the Colorado River Basin. The Upper Basin states have argued that Reclamation’s documents from the 1960s – 1980s identified positive results of weather modification.

This above section needs supporting references for the assertions made about seeding results, the benefit claim, and who are those “Upper Basin States”?  Otherwise these statements should be taken with extra caution.

1.5 Brief History of Federal and State Authorizations for Weather Modification 

The following is taken from Chisolm and Grimes (1979): 

In 1968, the Colorado River Basin Project Act of 1968 (Public Law 90-537) was passed by Congress to provide for the further comprehensive development of water resources of the Colorado River Basin and for the provision of additional and adequate water supplies for use in the upper as well as lower Colorado River Basin. Under Title II of this Act, the Secretary of the Interior was authorized to prepare and implement an augmentation plan to meet the water requirements of the new projects created by the Act (Central Arizona Project and Colorado River Storage Project), existing projects and water allotments, and the 1944 water treaty with Mexico. 

Augmentation was one of the main issues in the deliberation on the Act. The Act defines augmentation as, “ ‘augment’ or ‘augmentation’ when used herein with reference to water means to increase supply of the Colorado River system or its tributaries by introduction of water into the Colorado River system, which is in addition to the natural supply of the system.” The Statement of the Managers on the part of the House with regard to augmentation stated “all possible sources of water must be considered, including water conservation and salvage, weather modification, desalinization and importation from areas of surplus.”

The Colorado River Basin Pilot Project (CRBPP) was the Bureau’s first major effort on weather modification in Colorado under the auspices of Project Skywater and P. L. 90-537. The purpose of the Colorado River Basin Pilot Project was to provide for scientific and economic evaluation of precipitation augmentation technology and to increase precipitation. The specific objectives to be achieved were (l) to establish and operate a ground-based meteorological network in and near the San Juan Mountains of Colorado to provide data input in the selection of suitable storms for seeding, and (2) to establish and operate a ground-based silver iodide seeding system to increase snowfall in the project target area. The field phase of CRBPP began with the winter of 1969-1970 (installation of gauges and seeding generator siting) while the random seeding phase began with the 1970-71 season and ran through the 1974-75 season (not the 1973-74 season as the author stated).

Date corrections are needed from the original text, not a good sign of the author’s knowledge concerning the CRBPP.  What is incomprehensible is that the goal of replicating the large percentage increases in snowfall reported in three randomized experiments by the author’s former home institution, Colorado State University, is left out of this rationale for the CRBPP.  Surely, the author knew, also as a long term BOR cloud seeding division employee, that those experiments were the primary motivation for the BOR to spend $40-50 million (in 2023 dollars) on the CRBPP.

At about the time of completion of CRBPP in Colorado, the Bureau began funding Project Snowman in Utah. Project Snowman was conducted for the Bureau by Utah State University’s Water Research Laboratory. The objective of this four-year project was to develop cold-cloud seeding technology using airborne generators and ground-based generators located in the northern portion of the Wasatch Mountains.

References are also needed here.

The Bureau’s early work on precipitation augmentation in Colorado was based on a fairly extensive background of research activities. Three major research efforts in winter seeding contributed directly to the Bureau’s CRBPP project in the Upper Colorado River Basin. These were: 

  1. The National Science Foundation sponsored research experiments by Colorado State University at Climax, Colorado, during the 1960’s.

“1” above is not a sufficient description of the motivation for the CRBPP.  The Climax experiments were reported on numerous occasions in the peer-reviewed literature as cloud seeding successes when air mass temperatures were high (i. e., high 500 hPa and 700 hPa equivalent temperatures as by Grant and Mielke 1967u, Kahan et al. 1969u, Grant et al. 1969u, Mielke et al. 1970u, 1971u, among others).  The BOR had a LOT of peer-reviewed evidence on which to base the CRBPP and in particular, in the Grant et al. 1969u Interim Report to the BOR that described the results of the Climax I results, and the preliminary results of Climax II and the Wolf Creek Pass experiments.  The findings in these three experiments, as described by Grant et al. 1969u,  were remarkably supportive of one another.  Climax II was a confirmatory experiment; nothing was changed from Climax I.

2. The operational research funded by the State of Colorado during the 1960′ s at several mountain passes, particularly Wolf Creek Pass in the San Juan Mountains, and,

The Wolf Creek Pass experiment mentioned above was a six winter season,  fully RANDOMIZED  experiment where entire winter seasons were randomized.  This experiment was critical to where the CRBPP was located since it appeared to have produced more water than seeding had in northern Colorado where the Climax experiments took place.

3. The Bureau sponsored experiments in the Park Range near Steamboat Springs, Coloradoduring the late 1960’s.

Rhea et al.’s 1969u “Final Report” to the  BOR concerning the Park Range Project  is eventually cited by Reynold’s, but is not in Reynold’s references.  This report was a “heads up” on all the problems that would be “rediscovered” during the CRBPP (e.g, as reported in Willis and Rangno 1971u).

The results of the Colorado River Pilot Project indicated the need for further verification and improvement in technology before a large augmentation program could be undertaken again.

This is a vague description of the CRBPP results, perhaps intentionally so. Why not just say what happened for the reader right here in plain language?   “The results of the earlier CSU experiments could not be replicated in the CRBPP (Elliott et al. 1978u followed by a citation to the “Comments” on Elliott et al’s findings by Rangno and Hobbs 1980-the latter reference is contained in Reynold’s references but is not discussed in his review.   Later, it was discovered that those early optimistic CSU results and the microphysical foundation on which they rested on were all ersatz leaving no real basis for the CRBPP  (e.g., Mielke 1979u, Rangno 1979u, Hobbs and Rangno 1979u, Rhea 1983, Rangno and Hobbs 1987u, 1993, 1995a, u)”

The Wolf Creek Pass seeding effort was designed to test whether a viable signal in runoff from Wolf Creek Pass could be produced by seeding all winter.  The Wolf Creek Pass experiment, conducted from the winters of 1964/65 through 1969/70 produced stunning results when the three randomly chosen seeded seasons were compared with the long historical runoff record (Grant et al. 1969u, Morel-Seytoux and Saheli 1973u).  Furthermore, the results of seeding on  individual days during the seeded winters appeared to replicate the results of Climax I.  It doesn’t get any better than this for a trifecta of apparent cloud seeding successes!  

But, it was all a mirage (e.g., Rangno 1979u), which makes this story so interesting from a scientific viewpoint.

Thus, the Bureau’s research program continued.

Winter experiments were conducted outside of the Colorado River Basin at: Elk Mountain, Wyoming (University of Wyoming) Bridger Range, Montana (Montana State University) Jemez Mountains, New Mexico (New Mexico State University) Pyramid Lake Pilot Project (University of Nevada) In addition, the Bureau continued to provide supplemental funds to Colorado State University’s NSF research and to Utah State University’s state -sponsored research project. Through the Emergency Drought Act of 1977 the Bureau granted over $2 million to six states for supplemental support of their cloud seeding projects including over $1 million to the States of Colorado and Utah for cloud seeding in the Colorado River Basin. 

1.6 Current Policy Statements from American Meteorological Society and World Meteorological Organization on Efficacy of Winter Orographic Cloud Seeding 

The two leading organizations representing the atmospheric science scientific establishment, the World Meteorological Organization and the American Meteorological Society, have both issued policy statements on the efficacy of winter orographic cloud seeding. These are relevant to review given the NRC 2003 conclusions. 

The current statement from the World Meteorological Organization (WMO 2010) on weather modification in general and relating specifically to winter orographic cloud seeding efficacy is stated below. 

“The scientific status of weather modification, while steadily improving, still reflects limitations in the detailed understanding of cloud microphysics and precipitation formation, as well as inadequacies in accurate precipitation measurement. Governments and scientific institutions are urged to substantially increase their efforts in basic physics and chemistry research related to weather modification and related programmes in weather modification. Further testing and evaluation of physical concepts and seeding strategies are critically important. The acceptance of weather modification can only be improved by increasing the numbers of well executed experiments and building the base of positive scientific results.” 

“Cloud seeding has been used on both cold clouds, in which glaciogenic seeding aims to induce ice-phase precipitation, and warm clouds, where hygroscopic seeding aims to promote coalescence of water droplets. There is statistical evidence, supported by some observations, of precipitation enhancement from glaciogenic seeding of orographic supercooled liquid and mixed-phase clouds and of some clouds associated with frontal systems that contain supercooled liquid water. “ 

The current AMS policy statement (AMS 2010) does not address specifically the efficacy of winter orographic cloud seeding but much like the NRC 2003 report identifies uncertainty and risk with much the same conclusions. These are listed below. 

UNCERTAINTY – Planned weather modification programs benefit from a comprehensive understanding of the physical processes responsible for desired modification effects. Recent improvements in the composition and techniques for dispersion of seeding agents, observational technology, numerical cloud models, and in physical understanding of cloud processes permit evermore detailed design and targeting of planned weather modification effects, and more accurate specification of the range of anticipated responses. While effects are often immediately evident in simple situations, such as when cloud seeding is used to clear supercooled fog and low stratus cloud decks, in more complex cloud systems it is often difficult to determine a seeding effect on a cloud-by-cloud basis. In these more complex situations, large numbers of events must be analyzed to separate the response to cloud seeding from natural variability in cloud behavior. Rigorous attention to evaluation of both operational and research programs is needed to help develop more effective procedures and to improve understanding of the effects of cloud seeding. Research and operational programs should be designed in a way that will allow their physical and statistical evaluation. Any statistical assessment must be accompanied by physical evaluation to confirm that the statistical results can be attributed to the seeding through a well-understood chain of physical events. It should be noted, though, that in practice large potential benefits can warrant relatively small investments to conduct operational cloud seeding despite some uncertainty in the outcome. 

The text in blue font seems like PR, Dave, and should be updated due to the lack of proof of seeding induced increases in snow we now have. Neiburger (1969u, WMO Tech Note) warned that such thinking usually excludes the idea that seeding might result in decreases in precipitation in addition to mistargeting, faulty operations.  


RISK MANAGEMENT – Unintended consequences of cloud seeding, such as changes in precipitation or other environmental impacts downwind of a target area, have not been clearly demonstrated, but neither can they be ruled out. In addition, cloud seeding materials may not always be successfully targeted and may cause their intended effects in an area different than the desired target area. This brings us to the ethical concern that activities conducted for the benefit of some may have an undesirable impact on others; weather modification programs should be designed to minimize negative impacts.. At times unintended effects may cross political boundaries, so international cooperation may be needed in some regions. Precipitation augmentation through cloud seeding should be viewed cautiously as a drought-relief measure because opportunities to increase precipitation are reduced during droughts. A program of precipitation augmentation is more effective in cushioning the impact of drought if it is used as part of a water management strategy on a long-term basis, with continuity from year to year, whenever opportunities exist to build soil moisture, to improve cropland, and to increase water in storage. From time to time methods have been proposed for modifying extreme weather phenomena, such as seeding severe thunderstorms with aerosols to diminish tornado intensity, or seeding tropical cyclones to cause changes in their dynamics and steer them away from land and/or diminish their intensity. Some experimentation has taken place in these areas, but current knowledge of these complex weather systems is limited, and the physical basis by which seeding might influence their evolution is not well understood. Weather modification techniques other than cloud seeding have been used in various areas of the world for short periods of time to achieve goals similar to those of cloud seeding. Much less is known about the effects of these other techniques, and their scientific basis is even further from being demonstrated, either statistically or physically, than it is for cloud seeding. Application of weather modification methods that are not supported by statistically positive results combined with a well-understood physical chain of processes leading to these results, and that can also be replicated by numerical cloud modeling, should be discouraged.

Other organizations such as the North American Interstate Weather Modification Council, The Weather Modification Association, the American Society of Civil Engineers, and the Western States Water Council have also adopted policy statements or adopted resolutions relating to the use of weather modification for increasing snowpack and water supply. These are referenced in Ryan (2005) and will not be repeated here. Most if not all of these statements are much more positive in their support of the application of weather modification for enhancing snowpack and runoff despite the lack of evidence as reported in NRC 2003.

To the uninitiated reader to the field of weather modification/cloud seeding, it will seem odd that there are government entities that will pay huge sums of tax payer monies for cloud seeding with no viable evidence that it does anything, evidence being in the form of randomized experiments, the “gold standard” of scientific proof.  

Why would those entities take such chances?  

If you haven’t guessed by now, it’s because those government entities are telling their constituents directly or implicitly that they are doing SOMETHING about a drought.  It’s a great ploy, and usually works except in the minds of those who know the science.  

What science?  

Two modern randomized experiments testing to see if cloud seeding can increase precipitation in mountainous regions (Wyoming and in northern Israel) ended with  no indications that cloud seeding increased precipitation.  These null findings have been published by Rasmussen et al. 2018u for Wyoming, and by Benjamini et al. 2023u for Israel.  Now you know.  

Did the “null” finding reported by Rasmussen et al. 2018 terminate cloud seeding in Wyoming?  Of course  not.  It just looks too good to the public that you’re doing something about water needs.  

1.7 Generalized Concepts of Winter Orographic Cloud Seeding 

It is useful to review the general principles of winter orographic snowfall and whether this process could be modified or enhanced by artificial means. The basic physical concepts associated with seeding winter orographic clouds are not debated even though there is considerable debate over weather modification and its efficacy. These basic physical concepts are reviewed in the following section. There are several text books and encyclopedia articles available for a more in-depth discussion or broader overview of the physical basis of cloud seeding (Hess 1974; Dennis 1980; Dennis 1987; and Heymsfield 1992). 

Dennis in his (1980) Academy Press book, “Weather Modification by Cloud Seeding,” relied heavily on the 1977 BOR Monograph Number 1 (yes, it was deemed that important by the BOR to name it as NUMBER ONE),  became outdated almost immediately when external critics (guess who?) found serious flaws in that “meta-analysis.”     The BOR study, published in 1978u (Vardiman and Moore) was retracted in 1980  by Rottner et al. 1980 as critical “Comments” on their paper by, yep, Rangno and Hobbs (1980) were being published.  Thus, Dennis (1980) might be reconsidered as a reference here.  The BOR was too willing to believe in cloud seeding success mirages that led to this major embarrassment.

Too, much of the cloud seeding literature in Hess (1974) has been overturned in reanalyses or has not been replicated, as in the recent Wyoming and Israel experiments.  But, “hey,” you can read about global cooling in Hess (1974), thought to be underway at that time.

Figure 1.2 from Ludlam (1955), reproduced below, describes the process that remains to this day the fundamental conceptual model associated with winter orographic cloud seeding. Figure 1.2 shows a shallow orographic cloud, where the liquid condensate produced by forced assent over a mountain barrier is unable to be converted to snowfall before the air descends and evaporates in the lee of the mountain. During wintertime the freezing level (height of the 0oC isotherm) varies dependent on the origin of the air mass impinging on the mountain barrier.  This varies from north to south with the freezing level being lower in altitude at the northern latitudes of the western US and the inter-mountain west where the air masses that impact this area are usually modified maritime polar or continental polar.

and height allowing the crystals to grow at the expense of the cloud water that in (a) was lost to the lee, bringing this moisture down on the windward side of the mountain.

1.2a is the non-precipitating cloud that forms the low, demonstrable end of seeding potential.

The text in blue in the body of the paragraph may be true, but….. warm air masses during times of upper level ridges along the West Coast shunt warm air mass storms into the central and northern Rockies, so this “paradigm” often does not hold.  Surface temperatures may be well below freezing, but much higher temperatures usually exist aloft in those warm aloft regions of winter storms.  The Climax I experiment, for example, had numerous warm aloft storms overrunning colder air with west-northwest flow due to this synoptic scenario.   Quantification of this claim would have been very informative and would have pinned it down for the reader…and me!

Freezing levels are usually below ground level in mountainous regions except in the warmest storms. In the Ludlum model, it is assumed the orographic cloud has a significant depth of cloud below 0 oC and thus the cloud moisture is said to be supercooled. The critical uncertainty with regard to successful conversion of the unused cloud condensate to snowfall prior to passing over the crest is the location, duration, temperature and concentration of the supercooled liquid water (SLW).

As Ludlum describes it may take as much as 1500 seconds once artificial ice crystals are initiated to grow and fall out before passing to the lee of the mountain crest.  This can vary by several tens of minutes based on SLW concentration, temperature vertical profile and winds.

The process of crystal growth is almost always much fast than “as much as” 25 minutes to fallout cited by Ludlum  (e.g., Auer et al. 1969, Cooper and Vali 1981).

So the critical factors for achieving success are getting the seeding agent into the cloud at the right location where it will generate enough ice embryos such that they will utilize the available SLW prior to passing over the crest. There are many complex interactions that have made it very difficult to demonstrate the efficacy of winter orographic cloud seeding to the satisfaction of the scientific community. These factors are described in the following paragraphs. 

So true.

 1.7.1 The Initiation, Growth and Fallout of Snow in Winter Orographic Clouds Converting Supercooled Liquid Water (SLW) to Snow

Supercooled liquid water (SLW) in the atmosphere is made up of tiny cloud droplets that are colder than 0 oC. There are two processes in nature by which SLW in the atmosphere can freeze to initiate snowfall: 1. Heterogeneous nucleation or 2. Homogeneous nucleation. Heterogeneous nucleation occurs when the supercooled liquid drop comes in contact with what is called an ice nucleus (IN) that emulates the crystalline structure of ice and causes the droplet to freeze. These can be dust particles, biological particles or a combination of the two. These aerosols can come from as far away as Asia and Africa initiating cloud ice in orographic clouds in the western US (Cremean et al. 2013). They are made of very small particles of tenths of microns in size. They are most active at cloud top and tend to activate the growth of snowflakes from the top of the cloud down. The warmer the cloud top the less percentage of ice makes up the cloud (Cremean et al. 2013).

Sidebar:  An interesting feature, first observed in the 1950s (e.g., Cunningham 1957u) and afterward was the “upside down” storm structure where few ice crystals were found at low cloud top temperatures consisting mostly of supercooled liquid water with increasing ice crystal concentrations below the top. The increasing concentrations of ice crystals were mostly due to the fragmentation of delicate ice crystals. The most recent description of this scenario was by Rauber and Tokay (1991u) and Hobbs and Rangno (1985).

Lower down, within a km of the surface, ground observations have shown that riming and and aggregation occur that increase snowfall rates. This lower region near mountains cannot be sampled by aircraft if precipitation is falling and as a result, has mainly been documented  in ground observations (e.g, Hobbs 1975). Thus, aircraft observations can often be seen as under measuring ice particle concentrations in mountainous regions.  For example, we at the University of Washington often overflew shallow orographic clouds with liquid tops at >-10C with snow falling out underneath, but we couldn’t sample them because the tops were too close to the tops of the Cascade Mountains.

When clouds are dominated by warm rain processes, the aerosol makeup of the cloud is more sea salt and biological particles which act as condensation nuclei producing larger cloud droplets which grow to raindrops via collision coalescence. Homogeneous nucleation occurs when the air temperature drops below -40 oC and the water droplet spontaneously freezes without the aid of a nucleating agent. The most basic hypothesis in winter orographic cloud seeding is that in the presence of SLW droplets, ice crystals will grow at the expense of the drops. This means the drops will convert back to vapor allowing the crystals to grow by vapor deposition unless too many ice crystals have resulted from seeding in which case they might not grow at all. The driver for crystal growth is related to the concentration of SLW and the temperature regime of the SLW (Ryan et al. 1976; Heymsfield 1992; Pruppacher and Klett 1978).

In the presence of moderately high concentrations of SLW and with somewhat preferred growth temperatures (Ryan et al. 1976, Figure 1.3) enough of the initial ice crystals can grow and then begin to aggregate into larger flakes leading to higher fall speeds and earlier fall-out. If these artificial crystals encounter additional SLW as they fall back toward the mountain crest, the individual crystals or aggregates may collect these SLW drops (called riming) which will also increase the crystals fall-speed. If the naturally created ice crystals are unable to utilize all the available SLW, and some SLW evaporates to the lee of the mountain, the cloud is said to be less than 100% efficient. This provides the opportunity for the artificial injection of a nucleating agent to create the additional ice crystals necessary to bring the residual cloud water to the ground before it is lost to the lee of the mountain. This is the basic principles described in Ludlam’s model. 

Aerial Seeding window 

Ground based seeding temperatures 

General seeding window based on Figure 1.5 and observed SLW 

As Super and Heimbach (2005) noted, the frequency of occurrence of SLW is temperature dependent with higher frequencies and amounts at (higher) supercooled temperatures. This is true for all mountain ranges where SLW has been observed. There are two main reasons for this. First, the amount of water vapor in the atmosphere can be higher at warmer (higher) temperatures. Second, as the atmosphere cools and clouds form and reach temperatures lower than -10 oC, and especially at -20 oC, an abundance of natural ice can occur that depletes the supercooled cloud water. Thus, there is less SLW available for cloud seeding to enhance the natural precipitation process as the air approaches these temperatures. It should be noted that studies (Reinking et al. 2000; Super 2005) have found significantly higher amounts of SLW (.5 to 1 mm integrated SLW) in wave clouds during winter storms and noted that others had observed such amounts during brief periods in other western mountain locations. However, the overwhelming amount of observations utilizing microwave radiometers (Heggli and Rauber 1988; Huggins 2009; Super and Heimbach 2005), in-situ aircraft observations, and mountain top icing rate meters indicate that SLW is concentrated in the lowest 1000m along the windward slopes of mountain ranges during passing winter storms. The primary SLW zone rapidly dissipates downwind of the crest because of warming produced by subsidence and by depletion from conversion to snowfall (Boe and Super 1986; Rauber et al. 1986; Rangno 1986 (the rapid dissipation of SLW, one of my main points), Huggins 1995; Super 2005; Huggins 2009).  There are observations that confirm the simple conceptual model espoused by Ludlam when natural ice does not form. The location of many of the research studies referenced in this report along with other locations that will be referenced later in this report are shown in Figure 1.4b. One can compare these locations to Figure 1.4a which shows the location where operational winter orographic cloud seeding is conducted circa 2006 per Griffith et al. 2006. Coastally influenced areas would be west of the Sierra Nevada and Cascades while the intermountain region refers to areas east of these two ranges. 

The actual temperature relationship to SLW occurrence varies geographically. For the intermountain west, where the cloud drop size distributions are more numerous at the smaller drop sizes (10 to 15 microns; what is referred to as a continental drop size distribution), lower temperatures are reached before a sufficient number of natural ice crystals develop to utilize the available SLW. Thus, SLW can exist, at least briefly, at temperatures as low as -15 to -20 oC. Super and Heimbach (2005) provide a comprehensive review of SLW climatology in the intermountain west. 

In more coastal regions, such as the Sierra Nevada and Cascades, the drop size distribution can be broad (what is referred to as a maritime drop size distribution). The drops can begin to collide and coalesce because of the varying fall speeds of the drops with a broader distribution of cloud droplets (extending into and above 30 microns diameter). This leads to larger cloud drops (approaching drizzle size) that can be carried upslope into coastal mountains like the Cascades and Sierra Nevada ranges where just a few of these droplets can freeze leading to rime splintering or secondary ice-crystal production (Hallett and Mossop 1974; Dong and Hallett 1989; Mossop 1985). This can, and has been observed to lead to high concentrations of ice crystals with cloud temperatures warmer than -10 oC (Reinking 1978; Cooper 1986; Marwitz 1986; Hobbs and Rangno 1985; Rauber 1992).

Nieman et al 2005u reported  occurrences of the “warm rain” process in Northern California and Oregon were common.  Will cloud seeding increase precipitation if nature is providing rain via collisions with coalescence?

Other factors (Rango  (sic) 1986) can lead to high ice crystal concentrations with relatively high cloud top temperatures. Mixing of very dry air into cloud tops can initiate cloud droplet freezing (e.g., Koenig 1968; Hobbs and Rangno 1985). This has been observed in the Cascades, Sierra Nevada and southern Utah. In the post-frontal airmass, where most of the shallow orographic clouds exist, very dry air can exist above cloud top. This is caused by sinking air parcels in the region behind the upper-level jet-stream that usually passes just ahead of the surface cold front  (Heggli and Reynolds 1985). Thus the coastal mountain clouds will have a lesser degree of supercooling, meaning that the clouds will be only marginally supercooled as natural ice production will utilize the available SLW within moderately supercooled clouds. Reynolds (1995) documented that over an 8 year period in the northern Sierra Nevada, 80% of the hours reporting SLW from mountain-top icing rate meters were at temperatures warmer than -4 oC. Reynolds (1996) also reported that 70% of the hours with precipitation had icing (riming?) reported. Approximately 300 hours of icing were reported per season. However, some seasons had average temperatures during icing warmer than -2 oC which may be too warm for any known seeding agent to work effectively unless seeded aloft using aerial seeding. Studies examining mountain top temperatures in Colorado and Utah revealed that SLW in clouds is mildly supercooled in a large portion of all storm passages, which means clouds are too warm for effective AgI seeding (Super 2005). Refer to Figure 1.5 for activation levels of the various cloud seeding agents currently used or proposed.

Why aren’t supercooled non-precipitating clouds’ occurrences documented for whole seasons as in Ludlams’s simple case? Seems this information would form a great starting point that could determine how much seeding can unequivocally increase snow.  The reader would like to know.

There are many studies (Heggli et al. 1983; Boe and Super 1986; Rauber and Grant 1986; Heggli and Rauber 1988; Super and Huggins 1993; Super 2005; Huggins 2009) that state SLW within a cloud varies rather rapidly with time over any given point. Due to this variability in SLW, identifying seeding potential within winter orographic storms will require identification of the proper seeding agent and delivery technique and applied at the correct time and location (Hunter 2007; Huggins 2009). Huggins (2009) suggests that any cloud seeding program will necessarily be treating clouds that at any given time may not have sufficient SLW (when the seeding agent arrives) given its variability. This begs the question as to whether seeding in these situations may have negative impacts on snowfall production. This will be further discussed in Section 1.7.4. Even though the location of SLW concentrations is known, the exact lower threshold for SLW concentrations to be sufficient for enhancing snowfall has not been quantified. It is believed to be greater than .05 mm integrated in the vertical derived from microwave radiometers (threshold used by Super and Heimbach 2005 and Manton et al 2011). However, Murakami (2013) used .2 mm as the lower threshold for determining cloud seeding feasibility and theorized that .3mm was probably the minimum threshold for viable increases in orographic precipitation enhancement.

For what durations of this SLW threshold? Did those these researchers report how long it lasted?  Did they make any seasonal estimates of these occurrences?  The reader would want to know.

This is a critical question as frequency distributions of SLW concentrations from radiometer data (Reynolds 1988) indicate that 85% of the SLW reported were at concentrations below .2 mm (Figure 1.5).What constitutes a necessary and sufficient concentration of SLW for effective cloud seeding is still in debate. 

Several studies (Rosenfeld 2000; Givati and Rosenfeld 2004; Rosenfeld and Givati, 2006; Griffith et al. 2005; Hunter 2007) have described decreases in orographic precipitation due to pollution.

The above requires some exhaustive comments:

Reynolds was unaware that when the claims of Givati and Rosenfeld concerning air pollution were examined by external skeptics they have not been substantiated.   I think this same view should be taken with Givati and Rosenfeld (2006) for pollution effects on West Coast precipitation.  We need this latter study to be validated by an external skeptic!  Yes, I am excited here.

I suspect, as in the Givati and Rosenfeld’s (2005) Israel study, where more than 500 standard gauges and 82 or so recording gauges were available to cherry-pick whatever result one wants, this may well have been  done in the 2006 study.   Kessler et al. (2006u), in an evaluation of the Israeli operational seeding program wrote: “No supporting evidence was found for the thesis of Givati and Rosenfeld (2005) regarding the decline in the Orographic (sic) precipitations due to the increase of air pollution.”

The air pollution claims, while superficially credible except for their sudden hypothesized appearance in Israel after 1990 when operational seeding produced a slight indication of decreased rainfall (Kessler et al. 2006u), were also evaluated by several independent groups and scientists: Alpert et al. (2008u, 2009u); Halfon et al. (2009u); Levin 2009u.   The Givati and Rosenfeld (2005) claims were also addressed in a review by Ayers and Levin (2009u). All these independent re-analyses and reviews of the hypothesized effect of air pollution on rainfall found the argument that air pollution had canceled seeding-induced increases in rain in Israel unconvincing.   In the few cases that Dr. Rosenfeld’s papers have been reviewed by external skeptics, they don’t hold up.  Ask Prof. Levin, Tel Aviv University, Professor Sandra Yuter, North Carolina State University, Nathan Halfon, Tel Aviv University, or me.   Hence, Caveat Emptor!

This specifically impacts the collision coalescence process and what is called warm rain, i.e. no ice processes involved. These studies discuss that pollution can slow down the collision coalescence process by narrowing the drop-size distribution. This, in turn, slows down the warm rain process and would have the largest impacts in the low-elevation coastal ranges along the west coast where the freezing level is well above the elevations of the coastal mountains, i.e. around Los Angeles where it has been proposed to reduce precipitation. Typically the decrease in orographically enhanced precipitation is greatest downwind of a major metropolitan area that is producing pollution. Givati and Rosenfeld (2004) showed precipitation losses near orographic features downwind of coastal urban centers corresponding to 15-25% of the annual precipitation.

Caveat emptor re Givati and Rosenfeld’s findings!

This loss of precipitation can be greater than the gain claimed by precipitation enhancement techniques in portions of California (Hunter 2007). Hindman et al (2006) noted that the trend over the past 20 years, from cloud droplet measurements at Storm Peak in the northern Rockies, has shown a decrease in CCN and an increase in cloud drop size. The conclusion was a decrease in upwind CCN concentrations (less pollution) but no relationship was found with precipitation rate. Thus, the change in cloud droplet spectra was not impacting riming growth efficiency (Borys et al 2003). It was noted by Creamean (2013) that pollutants, such as from human activity, were found mostly in the boundary layer and with frequently higher concentrations preceding surface cold fronts. The pollutants become trapped in the stable air as the air warms aloft and surface flows tend to be from the southeast to east tapping polluted sources from the central valley of CA. Once the front passed, the air-mass off the ocean did not contain these pollutants. It is the post–frontal cloud systems that have been identified as the most seedable in the northern and central Sierra (Heggli and Reynolds, 1985). It is not anticipated that pollutants play a significant role in these post-frontal shallow orographic clouds.

It should be noted that a more recent survey article by Tanre’ et al (2009), reviewed the impact of aerosols on precipitation and concluded: “Even though we clearly see in measurements and in simulations the strong effect that aerosol particles have in cloud microphysics and development, we are not sure what is the magnitude or direction of the aerosol impact on precipitation and how it varies with meteorological conditions. Even the most informative measurements so far on the effect of aerosols on precipitation do not include simultaneous quantitative measurements of aerosols, cloud properties, precipitation and the full set of meteorological parameters.”

Thanks to Tanre’ et al. (2009)!

The current CALWATER II experiment running this winter in California is an attempt to provide such information.

(Did it?)

The main limitation is very similar to the problems inherent in quantifying the impacts of artificial seeding of winter orographic clouds. That is the observing systems that we apply to quantifying the impacts have large measurement uncertainties and are of a magnitude similar to the expected aerosol influence on precipitation. Tanre’ notes that satellite and radar measurements have 20-30% errors in the measurement of aerosol optical depth, while aircraft sampling in-cloud can introduce changes in the cloud that can compromise the utility of the aircraft observations. In-deed measurements of surface precipitation, especially snowfall water equivalent can have 10-15% measurement uncertainty given gauge location and thus exposure to wind, minimum threshold/resolution, and such problems as capping. These types of measurement uncertainties require longer term on-going statistical analyses to reduce the random noise in the observations much like is required for cloud seeding experiments, thus reducing the influence of measurement uncertainty so as to extract the small signal that might exist. Artificial Stimulation of Snowfall by Seeding Agents

Artificial stimulation of snowfall is conducted through the application of aerosols that mimic natural ice nuclei to enhance the heterogeneous freezing of available SLW or by chilling the air below -40 oC to initiate homogenous nucleation. It is well known that the effectiveness of the heterogeneous seeding agent is highly temperature dependent. Artificial cloud nucleating substances (AgI, CO2, Liquid propane, SNOWMAX) are dependent on the presence of SLW at temperatures slightly below 0 oC for CO2, propane, and SNOWMAX (Ward and Demott 1989) or below -5 C to -8 oC for AgI mixtures (Figure 1.6). 

Figure 1.6 – Seeding activation versus temperature for seeding agents that have been used or proposed

These seeding agents act in different ways. Solid or liquid CO2 and liquid propane work by homogenous nucleation. These seeding agents need to be directly released in the presence of SLW for them to be effective. AgI and SNOWMAX work by heterogeneous nucleation, meaning they mimic the structure of natural ice nuclei. They do not have to be released directly into cloud or SLW. The aerosol can be carried aloft into clouds and when it encounters SLW at the right temperatures will begin generating ice crystals by contact nucleation. As shown in Figure 1.6, SNOWMAX works at the warmer (higher) end of the SLW temperature spectrum and its effectiveness does not vary greatly with temperature. To the author’s knowledge, SNOWMAX is not used in any operational seeding program but is used almost exclusively for snowmaking at ski resorts. The effectiveness of AgI to nucleate ice crystals increases by orders of magnitude from -5 oC to -12 oC (Super 2005). It should be noted that under transient water supersaturations, AgI can activate more rapidly and at temperatures near -5 oC through the condensation freezing mechanism (Pitter and Finnegan 1987). Chai (1993) explained the only way AgI could have been an effective seeding agent in the Lake Almanor seeding experiment (Moony and Lunn 1969) was through the fast activating condensation freezing process.

Mooney and Lunn (1969)… The westerly case where it was reported there had been large increases in snow reported due to seeding, was not reported for Phase II of the Lake Almanor experiment (Bartlett et al. 1975u). This omission should be unsettling to any objective scientist.

If the AgI is burned below cloud base or at temperatures warmer than -5 o C, the aerosol will not produce sufficient ice embryos until temperatures colder than -8 oC are reached (Super and Heimbach 2005). Huggins (2009) found the best temperatures for SLW in the Bridger Range Experiment occurred at < -9 oC using AgI, which suggests the AgI acted through contact or deposition nucleation. The central reason to explore propane seeding is its characteristic to be effective in mildly supercooled clouds that would be too warm for AgI. Propane dispensers tend to be more reliable, less complicated and less expensive than AgI generators. SLW temperatures in CO frequently range from -4 to -13 oC depending upon location and elevation (Boe and Super 1986; Rauber and Grant 1986; Huggins 1995; Super 2005; Huggins 2009). Due to the mildly supercooled nature of some CO locations, propane could be a useful alternative to AgI generators (Boe and Super 1986; Hindman 1986). The cloud base in California is often warmer than 0 oC while the top of the SLW near the mountain crest is usually > -12 oC (Heggli et al. 1983; Heggli and Rauber 1988; Huggins 2009). This is why propane was adopted by Reynolds (1995) as the seeding agent of choice in the Lake Oroville Runoff Enhancement Program (LOREP) in northern California (see Figure 1.4b). 

Cloud base altitude is an important consideration when siting propane dispensers which must be in-cloud or just below cloud base (at ice saturation) to be effective (Super 2005). Super and Heimbach (2005) indicate that even in the intermountain region, a significant number of hours with SLW are at temperatures where the release of AgI at elevations below -5 oC and out of cloud would not reach elevations cold enough to activate a sufficient quantity of the AgI to effectively “seed” the cloud and produce meaningful increases in snowfall. Thus, the 300 to 600 hours of reported SLW over the intermountain region during the 5 month snowfall season would require a mixture of seeding delivery methods including a mixture of high elevation ground released AgI and liquid propane or seeding from multiple aircraft. 

All weather helicopters with ceilings above 20,000 feet ASL  might be useful for targeting small watersheds when shallower clouds are present.

1.7.2 Transport and Dispersion of Seeding Material Ground Releases 

Flow over complex terrain is not a simple and straightforward problem therefore making targeting a challenge. Trying to disperse AgI from ground based generators has proven to be very difficult (Super and Heimbach 2005). There are two critical issues here. One is whether a parcel of air starting out near the foothills or a valley location will be carried over the mountain in the prevailing wind direction or whether it will flow around the mountain. This is determined by the static stability of the air mass and the strength of the flow perpendicular to the mountain, often noted by the Froude number. When the velocity of the flow is strong enough to overcome the air parcels static stability, a Froude number greater than 1 is produced, meaning the parcel of air will pass over the mountain and not flow around the mountain. The depth of the boundary layer is also very important as ground based cloud seeding efforts are located within this layer. If AgI is released below cloud or at temperatures warmer than -5 oC, the aerosol will have to be carried up into the cloud to a level where the temperature is colder than -8 oC. If the boundary layer is shallow and does not allow the aerosol to reach the appropriate temperature level or that level is reached very near the crest of the mountain, there will be no impact on the windward slopes of the mountain. The depth of the boundary layer is a function of low level wind shear (Xue 2014), which is the change in direction or velocity of wind with height. The stronger the wind shear, the greater the depth of the boundary layer. Strong low level flow perpendicular to the mountain, along with strong wind shear and at times weak embedded convection, will provide the mechanism for lifting the aerosol up the mountain. This allows dispersal of the aerosol to seed more cloud volume. If the temperatures are cold enough and SLW is continuous, an increase in snowfall will occur on the windward slopes and increase the precipitation efficiency of the orographic cloud. The targeting issue has been described by many weather modification researchers (Super and Heimbach 2005; Reynolds 1988; Warburton et al. 1995a and b) as the single most critical issue that has compromised the success of both operational as well as research field projects. Again, reason to emphasize that effective cloud seeding is an engineering problem. 

It has been shown that ample seeded crystals with sufficient concentration need to be dispersed so that a substantial volume of cloud over the target is treated for more than trace snowfall rates to occur (Super 2005; Huggins 2009). The seeding material must be injected into the SLW in sufficient quantities to generate 50 to 100/L or more initial ice embryos. This will then utilize the available SLW and fall out of the cloud prior to the snowflakes passing over the summit of the mountain and sublimating in the lee of the mountain. An example of the use of a rather simple targeting model (GUIDE, Rauber et al , 1988) used in the Lake Oroville Runoff Enhancement Project (LOREP ) to target ground-based liquid propane seeding effects is shown in Figure 1.7. This project used the tracer SF6 co-released with the propane from two sites to validate the GUIDE and assure accurate targeting. The GUIDE plumes as shown both horizontally and vertically along with the vertical motion field from a locally released rawinsonde. Seeding from Valley Locations Many operational cloud seeding projects have placed AgI generators in valley locations as they are easily accessible and can be manually ignited when needed. However, a considerable body of evidence indicates valley released AgI plumes are often trapped by stable air (high static stability), especially when valley-based inversions are present (Langer et al. 1967; Rhea 1969-cited but does not appear in Reynolds references; Super 2005). Often times in past projects AgI plumes from valley located generators were not tracked sufficiently to determine exactly where the aerosol plumes drifted (Smith and Heffernan 1967; Super 2005). As noted earlier, this is a recurring issue that has been raised in many winter orographic cloud seeding articles ( Elliott et al. 1978u, Rangno 1979u; Reynolds 1988; Super 2005; Hunter 2007; Huggins 2009). The aerosols may pool in the valley or may move in a direction around the mountain, only to be carried aloft when the static stability of the airmass decreases and low level winds increase. This usually occurs near and behind the surface cold fronts associated with winter storms. Thus, the AgI aerosol may travel far distances from the target but is unlikely to have appreciable effects far from a target due to the low concentrations that eventuate after many hours or days of travel. Seeding from Airplanes or Helicopters

Seeding by aircraft can be an alternative mechanism in locations where there is insufficient time to activate the seeding agent and grow the crystals to sufficient size for fallout to occur on the windward slopes of the barrier. These situations mainly occur within coastal mountains where the SLW near the crest of the mountain is only slightly sub-cooled. Typically the clouds extend up to a kilometer above and well upwind of the crest such that cloud top temperatures are -6 oC to -8 oC or lower. In these situations, the aircraft or helicopter can fly (hover above) in the tops of the clouds and either drop crushed dry ice, AgI droppable flares, or ignite AgI wing-tip generators or stationary flares that will directly inject the seeding material into the cloud. The dispersion would be especially enhanced in the downwash below a helicopter. Using crushed dry ice or droppable flares will create a curtain of ice crystals some 1000 m below the aircraft. This will spread at a rate of 1-2 m/s dependent upon the amount of vertical wind shear (Borovikov et al. 1961u, Hill 1980; Reynolds 1988). For these seeding curtains to merge together over the intended target area, the length of the seed line cannot be more than 30 to 40 km long (Deshler et al. 1990). However, the watershed of a large river basin can be several hundred kilometers wide. One aircraft will treat only a small portion of the watershed (see Figure 1.8). In addition, the duration of the seeding aircraft is usually about 2 to 4 hours, with the possibility of the aircraft having to descend to deice several times during the seeding mission. Aircraft operations are also expensive. For these reasons, many operational seeding programs use ground based seeding platforms, even if they are only viable a small percentage of the time. 

1.7.4 Extended Area Effects fromWinter Orographic Cloud Seeding (ones that have not been sufficiently investigated for lucky draws/synoptic biases)

The reason why I added this to the title is that I deem this part of the survey the weakest part.  No one talks about how low the concentrations of AgI would be in far away, so-called downwind affected regions, and god save anyone who looks at synoptics for a bias! Meltesen et al.(1978) did look at synoptic bias for the claimed downwind seeding increases from Climax and look what they found;  a synoptic bias that produced the illusion of downwind increases in snow!

Hunter (2009) prepared an extensive literature review of the current state of knowledge on extra or extended area effects from winter orographic cloud seeding. The main impetus for this report was to present any documented evidence that determined that seeding on one mountain barrier resulted in a possible reduction of the amount of precipitation downwind. This has been coined “Robbing Peter to pay Paul”. Hunter provided the following table which is reproduced here (not all references are included in Section 6). In every case, the seeding agent was silver iodide. These results indicate that once the AgI nuclei are released into the atmosphere, they can remain active for many hours, if not several days. If pooled in high concentrations, the AgI nuclei can seed areas well away from the intended target areas. However, the impacts of these extra-area effects are just as uncertain as the increase documented in the primary target areas. That is, without strong physical observations to compare with rigorous statistical analyses, there is still a significant level of uncertainty as to the efficacy of seeding with AgI to increase precipitation within large areas outside the intended target area. 

Table 1.2 here

The little bit of seeding (hour long pulses) or in six h blocks during the last season of the Park Range Project, made this claim ludicrous.  By 1979 it was recognized that a Type I statistical error (Mielke 1979u) affected both Climax experiments.  One of the interesting facets of Climax I that  prevented the seeding researchers from recognizing a Type I error was attributing heavier snow on seeded days upwind of Climax to seeding at Climax (Kahan et al. 1969u) 

1.7.5 Statistical Analyses

Statistical analyses have been a key part of assessing past cloud seeding experiments. Credence has usually only been given to those experiments that have been randomized and run as a confirmatory experiment. Key historical projects such as Climax and the series of Israeli cloud seeding experiments run as confirmatory, and meeting or exceeding the level of statistical significance set out in the experimental design, have come under further scrutiny and found to suffer from what is called Type 1 errors (Mielke 1979u; Rhea 1983; Rangno and Hobbs 1987u, 1993; Rangno and Hobbs 1995a,u,  b; Rosenfeld 1997, Rangno and Hobbs 1997a,u, b u).

Rosenfeld’s (1997) “Comments” cited by Reynolds were replied to by Rangno and Hobbs (1997a,u) in short form, and “Comprehensively” at the Cloud and Aerosol Research Group’s website. This dual approach was favored by Professor Peter V. Hobbs.

Its surprising that Dr. Reynolds did not know of our responses to Dr. Rosenfeld’s many specious comments


Some background on the Israeli work I did: these many exchanges led the Israel National Water Authority to form an independent panel to evaluate its operational seeding program targeting Lake Kinneret (aka, Sea of Galilee), Israel’s primary water source (Y. Goldreich, 2018, personal communication). The expert panel  that was constituted could find no evidence of increased rain the in the catchment of Lake Kinneret between 1975 and 2002  (Kessler et al. 2006).  The independent panel’s findings reversed the optimistic findings of Nirel and Rosenfeld (1995) of a statistically significant 6% increases in rain through 1990. The panel could also not replicate the 6% increase reported by Nirel and Rosenfeld using the same control stations.  Here is what Kessler et al. (2006) reported in graphical form. 

Why is this Israeli discussion important in Reynolds’ review?

The preliminary findings shown in this figure caused Rosenfield to immediately look for an “out,” and with more than 500 standard gauges and 82 recording gauges in Israel (!)  he found it by cherry-picking and claiming what Reynolds suggests in his review: air pollution was decreasing rain as much as cloud seeding was increasing it.  Givati and Rosenfeld’s conclusions did not stand up to independent investigators as was documented earlier, nor by the subsequent investigations for California cited by Reynolds.

This is typical in scientific statistical testing. It is considered less incorrect to not detect a relationship when one exists rather than detect a relationship when one does not exist. Other statistical methods, such as the use of covariates, can be useful in determining the statistical success of seeding operations (Dennis 1980; Mielke et al. 1981; Gabriel 1999; Gabriel 2002; Huggins 2009). A problem common to the statistical method of historical regression is the assumption that climate has been stable over many decades (Hunter 2007) which is called stationarity, and not declaring covariates in advance of experimentation.

1.8 Summary 

From the information summarized above it is worth reviewing the key questions as outlined for winter orographic clouds as listed in Table 1.1. 

What is the location, duration, and degree of supercooling of cloud liquid water in winter orographic clouds? 

•Concentrated in the lowest km on the windward slopes of mountain (Super andHeimbach, 2005)

•Highly variable in space and time given fluctuations in wind speed/direction and naturalprecipitation processes.

•Higher concentrations and higher frequency of SLW at warmer (sic) (higher) temperatures for all mountain ranges•SLW >.05 mm vertical integrated has been used as lower threshold for cloudseeding initiation.

Are their man-made pollutants or natural aerosols/particulates impacting the target clouds that could modify the cloud droplet spectra/IN concentrations to impede seeding effectiveness? 

•Pollutants acting as CCN can narrow the droplet spectrum and slow down the collision coalescenceprocess (warm rain) reducing rainfall downwind of major pollution sources.(Rosenfeld 2000; Givati and Rosenfeld 2004; Givati and Rosenfeld 2005.  See earlier discussion of the latter report.)

•It was found in SCPP that SIP (secondary ice production) produced high ice concentrations at relatively high cloud top temperatures (-5 to -10 oC)

•If pollutants narrow the droplet spectrum, then pollutants in theory should reduce SIP.

Mossop (1978u) found that increases in small (<14 um diameter) droplets combined with those >23 um diameter increased the efficiency of the riming-splintering process.  So it is possible, with the presence of larger droplets say, due to seaborne or other large aerosols combined with pollution sources, that the Hallett-Mossop riming-splintering process is enhanced.

•If high concentrations of pollution produce high concentration of cloud droplets in a narrow size range, this could reduce riming and reduce snowfall on the windward slopes of narrow mountain ranges where growth times are critical.

•A more recent survey article on the role of pollution on clouds and precipitation (Tanre’, 2009) concluded it was still uncertain as to the magnitude of the impact of pollution or whether pollution increases or decreases precipitation based on the meteorological setting.

•Dust (Saharan and Gobi desert) and aerosols (bacteria) acting as IN can enhance natural s

Are their significant enough differences in maritime influenced winter orographic clouds versus continental orographic clouds that strongly influence the natural precipitation process? 

•Yes. Maritime clouds with broader drop size distributions are subject to SIP and thus clouds are more efficient at higher temperatures.

•Continental clouds have relatively more SLW at lower temperatures given the lack of SIP.

•Evidence of this is well-documented when one compares SCPP and Washington studies with interior mountain studies.

====================End of Comments and Corrections  by ALR==========================

References that were uncited in the Reynolds review but were mentioned in this “review and enhancement.”

Alpert, P., N. Halfon, and Z. Levin, 2008: Does air pollution really suppress precipitation in Israel?  J. Appl. Meteor. Climatology, 47, 943-948.

Alpert, P., N. Halfon, and Z. Levin, 2009:  Reply to Givati and Rosenfeld.  J. Appl. Meteor. Climatology, 48, 1751-1754.

Auer, A. H., D. L. Veal, and J. D. Marwitz, 1969: Observations of ice crystals and ice nuclei observations in stable cap clouds.  J. Atmos. Sci., 26, 1342-1343.

Ayers, G., and Levin, 2009:  Air pollution and precipitation.  In Clouds in the Perturbed Climate System.  Their Relationship to Energy Balance, Atmospheric Dynamics, and Precipitation. J. Heintzenberg and R. J. Charlson, Eds.  MIT Press, 369-399.

Bartlett, J. P.,  M. L. Mooney, and W. L. Scott, 1975:  Lake Almanor cloud seeding program.  Preprint, San Francisco Conference on weather modification, Amer. Meteor. Soc., 106-111.

Benjamini, Y, A. Givati, P. Khain, Y. Levi, D. Rosenfeld, U. Shamir, A. Siegel, A. Zipori, B. Ziv, and D. M. Steinberg, 2023:  The Israel 4 Cloud Seeding Experiment: Primary Results.   J. Appl. Meteor. Climate, 62, 317-327.

Borovikov, A. M., I. I. Gaivoronsky, E. G. Zak, V. V. Kostarev, I. P. Mazin, V. E. Minervin, A. Kh. Khrgian and S. M. Shmeter, 1961:  Cloud Physics. Gidrometeor. Izdatel. Leningrad. (Available from Office of Tech. Serv., U. S. Dept. of Commerce.)

Cooper, W. A., and G. Vali, 1981:  The origin of ice in mountain cap clouds.  J. Atmos. Sci., 38, 1244-1259.

Cunningham, R. M., 1957:  A discussion of generating cell observations with respect to the existence of freezing or sublimation nuclei.  In Artificial Stimulation of Rain, H. Weickmann, Ed.  Pergamon Press, NY.,  267-270.

Elliott, R. D., R. W. Shaffer, A. Court, and J. F. Hannaford, 1978:  Randomized cloud seeding in the San Juan Mountains, Colorado.  J. Appl. Meteor., 17, 1298–1318.

Foster, K. R., and P. W. Huber, 1997: Judging  Science–Scientific Knowledge and the Federal Courts.  The MIT Press, Cambridge, MA, 333pp.

Grant, L. O., and P. W. Mielke, Jr., 1967: A randomized cloud seeding experiment at Climax, Colorado 1960-1965.  Proc. Fifth Berkeley Symposium on Mathematical Statistics and Probability, Vol. 5, University of California Press, 115-131.

Grant, L. O., Chappell, C. F., Crow, L. W., Mielke, P. W., Jr., Rasmussen, J. L., Shobe, W. E., Stockwell, H., and R. A. Wykstra, 1969:  An operational adaptation program of weather modification for the Colorado River basin.  Interim report to the Bureau of Reclamation, Department of Atmospheric Sciences, Colorado State University, Fort Collins, 98pp.

Halfon, N., Z. Levin, P. Alpert, 2009:  Temporal rainfall fluctuations in Israel and their possible link to urban and air pollution effects.  Environ, Res. Lett., 4, 12pp. doi:10.1088/1748-9326/4/2/025001

Hobbs, P. V., and A. L. Rangno, 1979: Comments on the Climax randomized cloud seeding experiments.   J. Appl. Meteor., 18, 1233-1237.

Kahan, K. M., J. R. Stinson, and R. L. Eddy, 1969:  Progress in precipitation modification.  Bull. Amer. Meteor. Soc., 50, 206–214.

Kessler, A., A. Cohen, D. Sharon, 2003:  Analysis of the cloud seeding in Northern Israel.  Interim report submitted to the Israel Hydrology Institute and the Israel Water Management of the Ministry of Infrastructure.

Kessler, A., A. Cohen, D. Sharon, 2006:  Analysis of the cloud seeding in Northern Israel. Final report submitted to the Israel Hydrology Institute and the Israel Water Management of the Ministry of Infrastructure, In Hebrew with an English abstract. 117pp.

Levin, Z., 2009:  On the state of cloud seeding for rain enhancement.  Report to the Cyprus Institute on Energy, Environment and Water, 18pp.

Mielke, P. W., Jr., 1979:  Comment on field experimentation in weather modification.  J. Amer. Statist. Assoc., 74, 87–88,

Mielke, P. W., Jr., L. O. Grant, and C. F. Chappell, 1970: Elevation and spatial variation effects of wintertime orographic cloud seeding. J. Appl. Meteor., 9, 476–488; Corrigendum, 10, 842; Corrigendum, 15, 801.

Mielke, P. W., Jr., Grant, L. O., and C. F. Chappell, 1971:  An independent replication of the Climax wintertime orographic cloud seeding experiment.  J. Appl. Meteor., 10, 1198-1212.

Morel-Seytoux, H. J., and F. Saheli, 1973: Test of runoff increase due to precipitation management for the Colorado River Basin Pilot Project.  J. Appl. Meteor., 12, 322-337.

Mossop, S. C., 1978: The influence of the drop size distribution on the production of secondary ice particles during graupel growth. Quart J. Roy. Meteor. Soc., 104, 323-330.

Neiburger, M., 1969: Artificial Modification of Precipitation. W. M. O. Technical Note 105, 33pp.

Neiman, P. J., G. A. Wick, F. M. Ralph, B. E.  Martner, A. B. White, and D. E. Kingsmill, 2005:  Wintertime nonbrightband rain in California and Oregon during CALJET and PACJET:  Geographic, interannual and synoptic variability.  Mon. Wea. Rev., 133, 1199-1223.

Rangno, A. L., 1979:  A reanalysis of the Wolf Creek Pass cloud seeding experiment.   J. Appl. Meteor., 18, 579–605.

Rangno, A. L. and P. V. Hobbs, 1980: Comments on “Randomized cloud seeding in the San Juan Mountains, Colorado,” J. Applied Meteorology, 19, 346-350. 

Rangno, A. L., and P. V. Hobbs, 1987: A re-evaluation of the Climax cloud seeding experiments using NOAA published data.  J. Climate Appl. Meteor., 26,  757-762.

Rangno, A. L., and P. V. Hobbs, 1995a: Reply to Gabriel and Mielke.  J. Appl. Meteor., 34, 1233-1238.

Rangno, A. L. and P. V. Hobbs, 1997a: Reply to Rosenfeld.  J. Appl. Meteor., 36, 272-276.;2

Rangno, A. L. and P. V. Hobbs, 1997b: Comprehensive Reply to Rosenfeld, Cloud and Aerosol Research Group, Department of Atmospheric Sciences, University of Washington, 25pp.

Rasmussen, R. M., S. A. Tessendorf, L. Xue, C. Weeks, K. Ikeda, S. Landolt, D. Breed, T. Deshler, and B. Lawrence, 2018: Evaluation of the Wyoming Weather Modification Pilot Project (WWMPP) using two approaches: Traditional statistics and ensemble modeling. J. Appl. Meteoro. Climatol., 57, 2639–2660, D-17-0335.1.

Rauber, R. M., and A. Tokay, 1991:  An explanation for the existence of supercooled water at the top of cold clouds. J. Appl. Meteor., 48, 1005-1023.

Rhea, J. O., L. G. Davis, and P. T. Willis, 1969:  The Park Range Project.  Final Report to the Bureau of Reclamation, EG&G, Inc., Steamboat Springs, CO. 285 pp.

Rottner, D., L. Vardiman, and J. A. Moore, 1980: Reanalysis of “Generalized Criteria for Seeding Winter Orographic Clouds”, J. Appl. Meteor., 19, 622-626.

Vardiman, L, and J. A. Moore, 1978: Generalized criteria for seeding winter orographic clouds. J. Appl. Meteor., 17, 1769-1777.

A Review and Enhancement of Chapter 8 in the book, “Aerosol Pollution Impacts on Precipitation:  A Scientific Review” 


Below is the impressive list of “Scientific Reviewers” of this volume before this belated review by yours truly happened, ones listed in the 2009 Springer book,  “Aerosol Pollution Impacts on Precipitation:  A Scientific Review.”  The authors of this book, including Chapter 8, had to review an enormous amount of literature which the reviewers also had to know in great detail.

From a reading of this book in those areas of my expertise, such a task is too much despite the authors’ valiant efforts to “get it right.”  Chapter 8  is an example of the problem of having too much to review and not enough time to scrutinize the details of so much literature in one topic.  Chapter 8 is well-written, most of the necessary citations are in it that help the reader to understand the topic.    It does an outstanding job of making a case about the, “Parallels and Contrasts” in deliberate seeding and aerosol pollution.  That is,  except for those elements in Chapter 8 that I am perhaps, a little too familiar with and feel must be addressed in this VERY belated review.

“Too familiar?”

That’s what happens to someone who has spent thousands of volunteer hours (crackpot alert!) rectifying faulty cloud seeding and cloud claims in peer-reviewed journal articles because he felt, “Someone has to do something about this!” (Second crackpot alert, possibly with megalomaniacal implications.)

It goes without saying that I was not asked to review Chapter 8 before it was published.  This would have made these comments unnecessary.  I was well known by the authors of this review as an expert on clouds, cloud seeding, and the weather in the two regions where landmark experiments are reviewed in Chapter 8; those in Colorado and Israel .   With Professor Peter V.  Hobbs in tow, I dissected those landmark experiments in Colorado and Israel and showed they were, as Foster and Huber (1997) described faulty science,  “scientific mirages.”  In fact, they were “low-hanging fruit” that poor peer reviews of manuscripts had let in the journals.  It didn’t take a genius to unravel them.

I read this chapter only recently after I was given the book by one of its authors.  I wondered if Chapter 8 had been reviewed at all by any of the illustrious reviewers listed by Springer since some oversights are so egregious.  However, I was pleased to see that almost all of my work with Prof. Hobbs on those benchmark experiments was cited, except the one I deemed most important.  Odd.

Some background 

Chapter 8 was originally assigned to Prof. Peter V. Hobbs, the director of my group at the University of Washington.  He was going to use portions of a rejected manuscript of mine on cloud seeding  and peer-review entitled, “Cloud Seeding and the Journal Barriers to Faulty Claims: Closing the Gaps.”  He described the segments he was going to use, the rise and fall of the Colorado and Israeli cloud seeding experiments, as, “pretty good.”   Peter was not easy to please.  That was the highest compliment I had ever received from him for my writing.   The manuscript, submitted in 1997,  was ultimately rejected in 1999 by the Bull. Amer. Meteor. Soc., I. Abrams, Editor,  and again in an updated version by  Advances in Meteorology in 2017 as “not the kind of paper we were looking for” in their issue on weather modification (L. Xue, Editor, personal communication).    But maybe its the kind you were looking for!  So, in a sense that manuscript has been rejected twice, sometimes the sign of something especially good.   (Off topic! Get Back, “Jojo,” as the Beatles sang.

Due to pancreatic cancer, Prof. Hobbs was unable to do this piece chapter and Prof. William R. Cotton, Colorado State University, who later has become a close friend,  took over with the additional “contributors” according to Springer,  Dean Terblanche, Zev Levin, Roelof Bruintjes, and Peter Hobbs, as listed by Springer, and all of whom I greatly admire, making these comments “difficult;” “Why am I doing this?”  Etc.

For review purposes, I have copied under the rubric of “fair use,” only those portions of Chapter 8 relevant to my expertise.   To repeat, overall, its a good review.  However, I have added commentaries in a red font following the original statements of the authors (black font) that need clarification, correction, or additions.  References to relevant articles that went uncited in Chapter 8 have been added at the end of this review and are appended with a “u” for uncited.  I have added after those all the references that WERE cited in this review and appear in the original text.  Mielke (1976) cited by the authors, does not appear in the list of their references.


List of illustrious reviewers of the Springer volume:

Chairperson: Dr.George IsaacEnvironment Canada.                       (Name, affiliation, country).

Ayers, Greg,  CSIRO Marine and Atmospheric Research, Australia

Barth, Mary, National Center of Atmospheric Research, USA

Bormann, Stephan,  Johannes-Gutenberg-University, Germany

Choularton, Thomas, University of Manchester, UK.

DeMott, Paul, Colorado State University, USA.

Flossmann, Andrea, Laboratoirede Mitiorologie Physique/OPGC Universiti: Blaise Pascal/C RS, France

Kahn, Ralph, Jet Propulsion Laboratory, USA

Khain, Alexander, The Hebrew University ofJerusalem, Israel

Leaitch, Richard, Environment Canada, Canada

Pandis, Spyros, University of Patras, Greece

Rosenfeld, Daniel, The Hebrew University ofJerusalem, Israel.

Ryan, Brian, CSIRO Marine and Atmospheric Research, Australia

Twohy, Cynthia, Oregon State University, USA.

Vali, Gabor, University of Wyoming, USA.

Yau,  Peter, McGill University, Canada

Zipser, Ed, University of Utah, USA


….and now, very belatedly reviewing Chapter 8, yours truly, the less illustrious,  Arthur L. Rangno,  retiree,                                                                                                                                                                                                Research Scientist IV, Cloud and Aerosol Research Group, Atmospheric Sciences Department, University of Washington, USA:


Chapter 8 in Aerosol Impacts on Precipitation:“Parallels and Contrasts Between Deliberate Cloud Seeding and Aerosol Pollution Effects”

8.1    Deliberate cloud seeding, with the goal of increasing precipitation by the injection of specific types of particles into clouds, has been pursued for over 50 years. Efforts to understand theprocesses involved have led to a significant body of knowledge about clouds and about the effects ofthe seeding aerosol. A number of projects focused on the statistical evaluation of whether a seeding effect can be distinguished in the presence of considerable natural variability. Both the knowledge gained from these experiments, and the awareness of the limitations in that understanding, are relevant to the general question of aerosol effects on precipitation. Definite proof from the seeding projects for an induced increase in precipitation as a result of the addition of seeding material to the clouds would represent a powerful demonstration of at least one type of dominant aerosol­ precipitation link in the clouds involved. Therefore, in this chapter we review the fundamental conceptsof cloud seeding and overview the parallels and contrasts between evaluations of deliberate and inadvertent modification of precipitation by aerosols. It is not our intent to provide a comprehensive assessment of the current status of cloud seeding research. We direct the reader to more compre­hensive weather modification assessments in NRC (2003), Cotton and Pielke (2007), Silverman (2001, 2003),and Garstang et al. (2005).

Deliberate cloud seeding experiments can be divided into two broad categories: glaciogenic seeding and hygroscopic seeding. Glaciogenic seeding occurs when ice-producing materials (e.g. dry ice (solid CO2), silver iodide, liquid propane etc.) are injected into a supercooled cloud for the purpose of stimulating precipitation by the ice particle mechanism (see Sect. 2.2). The underlying hypothesis for glaciogenic seeding is that there is commonly a deficiency of natural ice nuclei and therefore insufficient ice particles for the cloud to produce precipitation as efficiently as it would in the absence of seeding.

The second category of artificial seeding experiments is referred to as hygroscopic seeding. In the past this type of seeding was usually used for rain enhancement from warm clouds (see Cotton 1982 for a review of early hygroscopic seeding research).

However, more recently this type of seeding has been applied to mixed phase clouds as well. The goal of this type of seeding is to increase the concentration of collector drops that can grow efficiently into raindrops by collecting smaller droplets and by enhancing the formation of frozen raindrops and graupel particles. This is done by injecting into a cloud (generally at cloud base) large or giant hygroscopic particles (e.g., salt powders) that can grow rapidly by the condensation of water vapour to produce collector drops (see Sect. 2.3).

Static Glaciogenic Cloud Seeding

Static cloud seeding refers to the use of glaciogenic materials to modify the microstructures ofsupercooled clouds and precipitation. Many hundreds of such experiments have been carried over the past 50 years or so. Some are operational cloud seeding experiments (many of which are still being carried out around the world) which rarely provide sufficient information to decide whether or not they modified either clouds or precipitation. Others are well designed scientific experiments that provide extensive measurements and modeling studies that permit an assessment of whether artificial seeding modified cloud structures and, if the seeding was randomized, the effects of the seeding on precipitation. While there still is some debate of what constitutes firm “proof”(see NRC 2003; Garstang et al. 2005) that seeding affects precipitation, generally it is required that both strong physical evidence of appropriate modifications to cloud structures and highly significant statistical evidence be obtained.

My comprehensive, “critical” review and enhancement of NRC 2003 is here.  Compared to the 1973 NRC review, the NRC 2003 one was merely a superstructure, a Hollywood movie set, not the real deal.  

The reason?  

Too much literature to review in depth even for the illustrious authors of the NRC 2003 report.   Professor Garstang did ask my boss, Prof. Peter V. Hobbs to participate in the 2003 review, but he declined the offer telling me that it would be better if we “commented” on the 2003 review after it was published if necessary.  I nodded and went back to my desk.  Peter usually knew best.  Fate intervened.  Peter came down with pancreatic cancer and our review  of the 2003 report never happened until I got to it years later.

  • Glaciogenic Seeding of Cumulus Clouds

The static seeding concept has been applied to supercooled cumulus clouds and tested in a variety of regions. Two landmark experiments (Israeli I and Israeli II), carried out in Israel, were described in the peer-reviewed literature. The experiments were carried out by researchers at the Hebrew University of Jerusalem (HUJ), hereafter the experimenters. These two experiments were the foundation for the general view that under appropriate conditions, cloud seeding increases precipitation (e.g. N.R.C. 1973; Sax et al. 1975; Tukey et al. 1978a, b; Simpson 1979; Dennis 1980; Mason 1980,1982; Kerr 1982; Silverman 1986; Braham 1986; Cotton 1986a, b; Cotton and Pielke 1992, 1997; Young1993).

Nonetheless, reanalysis of those experiments by Rangno and Hobbs (1993-sic) suggested that the appearance of seeding-caused increases in rainfall in the Israel I experiment was due to “lucky draws” or a Type I statistical error.

The correct year for Rangno and Hobbs is 1995, not 1993 .   Having the wrong year in a reference is a not a good sign right off the bat.  

The first evidence for a lucky draw in Israeli I was presented by Wurtele (1971u) when she reported that the little seeded Buffer Zone between the two targets exhibited the greatest statistical significance in rainfall in either target on Center seeded days.  Wurtele (1971u) quoted the Israeli I chief meteorologist that the Buffer Zone could only have been inadvertently seeded but 5-10% of the time, and “probably less.”  Wurtele should have been cited.  The wind analysis when rain was falling at the launch site near the BZ in Rangno and Hobbs (1995) supports the chief meteorologist’s view.  It would have taken a very bad pilot to have seeded the BZ if he had been instructed not to.

Furthermore, Rangno and Hobbs (1993 sic) argued that during Israel II naturally heavy rainfall over a wide region encompassing the north target area gave the appearance that seeding caused increases in rainfall over the north target area.

The first evidence for naturally heavy rain over a wide region in Israel II, including both targets on north target seeded days, was presented by Gabriel and Rosenfeld (1990u), a critical article  that somehow that went uncited by the authors of Chapter 8.   Gabriel and Rosenfeld stated that the degree of heavy rain on north target seeded days in the south target, from a historical study, was “clearly statistically significant.” 

Rangno and Hobbs (1995) added to that evidence by analyzing rainfall over wide region that included Lebanon and Jordan on north target seeded days.  The Rangno and Hobbs (1995) analysis corroborated the statement by Gabriel and Rosenfeld (1990) concerning a lopsided draw on north target seeded days of Israeli II that affected most of Israel.  In fact, the greatest apparent effect of cloud seeding on north target seeded days was in the south target at Jerusalem (Rangno and Hobbs 1995)!

Deeply troubling, too,  is why the “full results” of the Israeli II experiment by Gabriel and Rosenfeld (1990u) was not cited in a supposed review of those experiments.  The null result of the “full analysis” of Israel II which incorporated random seeding in the South target,  had been omitted in previous reporting by Gagin and Neumann (1976u, 1981).  The “full” results reported by Gabriel and Rosenfeld (1990u) was an extremely important development:  Israeli II had not replicated Israeli I when evaluated in the same way.  Furthermore, the a priori design of Israeli II specified by the Israel Rain Committee mandated that a crossover evaluation be carried out (Silverman 2001).

However, the null result of Israeli II left some questions in the minds of Gabriel and Rosenfeld (1990u).  Were actual rain increases in the north canceled out by decreases in rain on seeded days in the south target resulting in a null overall result?

This idea was later posited by Rosenfeld and Farbstein (1992) as a valid explanation and the disparate results was attributed to dust/haze.  This hypothesis ignored the fact that unusually heavy rain fell on the south target when the north was being seeded.   This left little chance for the south target’s seeded days to overcome this lopsided disadvantage, thus  leaving the impression that seeding had decreased rainfall when rainfall on the control and seeded days in the south target were compared.  Why this was not clear remains a puzzle.

At the same time, lower natural rainfall in the region encompassing the south target area gave the appearance that seeding decreased rainfall over that target area. But this speculation could not explain the positive effect when the north target area was evaluated against the north upwind control area.

Levin et al. 2010u (and unavailable to these authors) also reanalyzed Israeli II and found that a synoptic bias had produced the misperception of seeding effects downwind from the coastal control region mentioned above.    Levin et al’s 2010u conclusions corroborated the Rangno and Hobbs (1995) evaluation of Israeli II described inappropriately as “speculation” by the authors of Chapter 8.  

Details of this controversy can be found in the March 1997 issue of the Journal of Applied Meteorology (Rosenfeld 1997; Rangno and Hobbs 1997a; Dennis and Orville 1997; Rangno and Hobbs1997b; Woodley 1997; Rangno and Hobbs 1997c;  Ben-Zvi 1997; Rangno and Hobbs 1997d; Rangno and Hobbs 1997e). Some of these responses clarified issues; others have left a number of questions unanswered.

The authors should have indicated for the reader what questions were left unanswered.  

However, the exchanges between pro-seeding partisans and Rangno and Hobbs (1997) were extremely important because they led the Israel National Water Authority to form an independent panel of experts to ascertain what the result of operational seeding of the watersheds around Lake Kinneret (aka, Sea of Galilee) was over the decades.  Operational seeding began during the 1975/76 rain season.

The reports of the independent panel (Kessler et al. 2002u, 2006u) were apparently unknown to the authors of this review.  Key elements of the final 2006 report were reprised by Sharon et al. (2008u):  Twenty-seven winter seasons  (75/76 through 01/02)  of operational seeding had not led to an indication that rain had been increased, due to cloud seeding,  an astounding result considering the cost of seeding for so long a period.

Below is a graphical presentation of the independent panel’s findings in their 2006 final report:

Figure 1. The results of operational seeding on the watersheds of Lake Kinneret (aka, Sea of Galilee) as reported by Kessler et al. 2006.  (a) is that result of seeding on rainfall reported by Nirel and Rosenfeld (1995), b-d are the results found for various periods, including the very same era evaluated by Nirel and Rosenfeld (1995).[1]


[1] The findings of Kessler were challenged by seeding partisans at the HUJ and who claimed that “air pollution” was decreasing rain as much as cloud seeding was increasing it.  While this was a convenient explanation, it was not found credible by many subsequent independent investigators, including by Kessler et al. (2006).

—————————continuing with Chapter 8————–

8 Deliberate Cloud Seeding and Aerosol Pollution Effects

It is interesting to note that in the Israeli experiments the effects of artificial seeding with silver iodide appeared to be an increase in the duration of precipi­ tation, with little if any effect on the intensity of precipitation (Gagin 1986; Gagin and Gabriel 1987), a finding compatible with the “static” seeding hypothesis.

The ersatz Colorado State University cloud seeding experiment results had exactly the same outcome as those described above in Israel.  In retrospect, the duration findings from both the Colorado and Israeli scientists were huge red flags that a natural bias on seeded days had occurred in these experiments as was shown in later reanalyses by external skeptics (e.g., Rhea 1983u, Rangno and Hobbs 1987).

Givati and Rosenfeld (2005) wrote, “that cloud seeding with silver iodide enhances precipitation especially where the orographic enhancement factor (see Chapter 6) was the largest. Likewise, the pollution effects reduced precipitation by the greatest amount at the same regions”. They suggestedthat this is because the shallow and short-living orographic clouds are particularly susceptible to such impacts. This suggests that attempts to alter winter precipitation should be concentrated on orographic clouds. Or interpreted in terms of inadvertent modification of clouds; winter orographic clouds may be the most susceptible to precipitation modification by pollution.

The Israeli “experimenters,” who cost their government so much in wasted cloud seeding effort, could not walk away and apologize for their misguided findings and withheld results.  So Givati and Rosenfeld (2005) generated the argument that pollution was exactly canceling out cloud seeding effects!  Of course, the air pollution argument was nonsense, the result of cherry picking amid the 500 or so Israeli rain gauges in Israel.   Here’s what the uncited Kessler et al. (2006u) report had to say about the Givati and Rosenfeld (2005) claims about air pollution:

No supporting evidence was found for the thesis of Givati and Rosenfeld (2005) regarding the decline in the Orographic precipitations (sic) due to the increase of air pollution.”

The air pollution claims by Givati and Rosenfeld (2005), while superficially credible,  except for their sudden hypothesized appearance that canceled out cloud seeding effects, were also evaluated by several independent groups and scientists in later publications not available to the authors of this review:  Alpert et al. (2008u); Halfon et al. (2009u);  Levin (2009u), Ayers and Levin (2009u).  All these independent re-analyses and reviews of the hypothesized effect of air pollution on rainfall found the argument that air pollution had canceled seeding-induced increases in rain unconvincing.

This also suggests that the conceptual model on which the Israeli cloud seeding experiments was based is not exactly as postulated. The seeding was originally aimed at the convective clouds that formed over the narrow coastal plain, with the intent of nucleating ice crystals and forming graupel earlier in the cloud life cycle (Gagin and Neumann 1974), thus leading to increased rainfall in the catchment basin of the Sea of Galilee to the east of the Galilee Mountains. However, the report of Givati and Rosenfeld (2005) concluded that “cloud seeding did not enhance the convective precipitation, but rather increased the orographic precipitation on the upwind side of the Mountains, probably by the Bergeron-Findeisen process.”

The above is not what Kessler et al. (2006u) concluded.   It was a shame that the authors did not know about Kessler et al.’s report.

To update this review, the idea posited by Rosenfeld and Givati (2005) about seeding orographic clouds, promoted by these authors, was tested in Israel-4, a seven season randomized experiment (Benjamini et al. 2023u).  Seeding in the orographic north of Israel resulted in no viable effect on rainfall.  This should not be surprising.

The lack of enhancement of the convective clouds in Israel might be explained by their tendency to mature and dissipate inland during the winter storms. Seeding of mature convective clouds cannot affect them much. The lack of enhancement is also consistent with the microphysically maritime nature of the convective clouds.

The authors seem to be unaware that for decades the cloud seeding experimenters had reported in their many publications that the clouds of Israel were “continental” in nature (e.g., Gagin and Neumann 1974, 1976u, Gagin 1975u), that is, they contained high droplet concentrations that made them extremely “un-maritime.”  This in turn helped generate scientific consensus that seeding such clouds had produced viable results on rainfall  in Israeli I and Israeli II because it was hard for them to rain and needed cloud seeding  (e.g., Kerr 1982, Silverman 1986, Dennis 1989).

This appears to be caused mainly due to the natural hygroscopic seeding by sea spray or mineral dust particles coated with soluble material (Levin et al.1996, 2005) in the winter storms that enhance the warm precipitation (Rosenfeld et al. 2001) as well as promoting the formation of ice hydrometeors that is followed by ice multiplication (Hallett and Mossop 1974).

In a surprising oversight in a supposed “scientific review,” the authors do not cite Rangno (1988) who described so long ago the clouds of Israel as we know them today; ones that rain via warm rain processes and precipitate regularly via the ice process when top temperatures are >-10°C, all contrary to the many reports of the cloud seeding experimenters (e.g., Gagin 1986).

Moreover, it has not been satisfactorily determined why the Israeli cloud seeding experimenters could not discern the natural precipitating characteristics of their clouds with all the tools available to them for so many decades.  Did the wind not blow over the Mediterranean during Israeli I and II, thus did not “maritimize” clouds when Prof. Gagin was observing them with his radars and sampling them with his research aircraft?

I spent 11 weeks in Israel from early January through mid-March 1986 studying the precipitating nature of Israeli clouds. I spoke with Israel Meteorological Service forecasters, and the chief forecaster of the Israeli randomized experiments.   Not surprisingly, they were all aware of the natural character of their rain clouds that so eluded the cloud seeding researchers at the HUJ; faulty descriptions of clouds were published by HUJ seeding researchers repeatedly in peer-reviewed journals.  How did this happen?

These suggestions are supported by the results of glaciogenic cloud seeding in Tasmania, which targeted a hilly area by seeding along an upwind coastline. The seeding in Tasmania was shown to enhance precipitation from the stratiform orographic clouds, but not from the convective clouds (Ryan and King 1997). This is consistent with the microphysical conclusions of Rangno and Hobbs (1993 sic), who asserted that, cloud seeding as done in Israel could not have possibly caused the statistically documented rain enhancement from the convective clouds there.

Again, the correct year for Rangno and Hobbs is 1995.  

The minimal amount of cloud seeding in Israeli I should have been discussed. The experimenters realized this post facto of Israel-1 and added a second seeding aircraft and no less than 42 ground generators (NRC 1973) when conducting Israel II.  The difference in released seeding material in Israeli II from the ~1000 grams released in all of Israeli I (Gabriel and Neumann (1967) has to be stupefying and raises questions.

Do the authors of this chapter really think that only 70 h of line seeding by a single aircraft upwind of each target per whole Israeli rain season could have produced a statistically significant result in rainfall in Israeli I?  Do they know that the coverage of convective clouds with rising air below cloud base is spotty,  that the rain that comes into Israel from the Mediterranean are “tangled masses” in various life cycle stages  (as described by Neumann et al. 1967)? 

Recently, Givati and Rosenfeld (2005) carried out a study in which the effects of pollution on rainfall suppression in orographic clouds were separated from the effects of cloud seeding in Israel. They concluded that the two effects have the opposite influence on rainfall, demonstrating the sensitivity of clouds to anthropogenic aerosols of different kinds. By analyzing the rainfall amounts in northern Israel during the last 53 years during days in which no seeding was carried out, they observed a decreasing trend of the orographic factor R0 (discussed in Chapter 6) with time from the beginning of the study. They associated this decrease with the increase in aerosol pollution. The same trend, but shifted upward by 12-14%, was observed for days in which seeding was carried out. Thus, it appears that the opposing effects of air pollution and seeding appear to have nearly canceled each other.

The air pollution canceling cloud seeding claims by Rosenfeld and colleagues have not been deemed credible to those who have investigated them, listed previously.  

Another noteworthy experiment was carried out in the high plains of the U.S. (High Plains Experiment (HIPLEX-1) Smith et al.(1984).Analysis of this experiment revealed the important result that after just 5 min, there was no statistically significant difference in the precipitation between seeded and non-seeded clouds, (Mielke et al. 1984). Cooper and Lawson( 1984) found that while high ice crystal concentrations were produced in the clouds by seeding, the cloud droplet region where the crystals formed evaporated too quickly for the incipient artificially produced ice crystals to grow to appreciable sizes. Instead, they formed low density, unrimed aggregates having the water equivalent of only drizzle drops, which were too small to reach the ground before evaporating. Schemenauer and Tsonis( 1985) affirmed the findings of Cooper and Lawson in a reanalysisof the HIPLEX data emphasizing their own earlier findings (Isaac et al. 1982) that cloud lifetimes were too short in the HIPLEX domain for seeding to have been effective in the clouds targeted for seeding (i.e. Those with tops warmer than -12°C). Although the experiment failed to demonstrate statistically all the hypothesized steps, the problems could be traced to the physical short lifetimes of the clouds (Cooper and Lawson 1984; Schemenauer and Tsonis 1985). This in itself is a significant result that shows the ability of physical measurements and studies to provide an understanding of the underlying processes in each experiment. The results suggested that a more limited window of opportunity exists for precipitation enhancement than was thought previously.  Cotton and Pielke (1995) summarized this window of opportunity as being limited to: Clouds that are relatively cold-based and continental; Clouds with top temperatures in the range -1O° to-25°C, and a timescale confined to the availability of significant supercooled water before depletion by entrainment and natural precipitation processes.

Today, this window would even be viewed as too large, since many cold based continental clouds with tops>-25°C have copious ice particle concentrations(e.g., Auer et al. 1969u, Cooper and Saunders 1980u, Cooper and Vali 1981u, Grant et al. 1982u.  These references were added to make them more appropriate for inland mountain locations). The HIPLEX results also indicated that small clouds make little contribution to rainfall.

This begs the question, should we expect a similar window of effectiveness for inadvertent IN pollution?

 8.1.1. Seeding Winter Orographic Clouds

The static mode of cloud seeding has also been applied to orographic clouds. Precipitation enhancement of orographic clouds by cloud seeding has several advantages over cumulus clouds. The clouds are persistent features that produce precipitation even in the absence of large-scale meteorological disturbances. Much of the precipitation is spatially confined to high mountainous regions thus making it easier to set up dense ground based seeding and observational networks. Moreover, orographic clouds are less susceptible to a “time window” as they are steady clouds that offer a greater opportunity for successful precipitation enhancement than cumulus clouds. A time window of a different type does exist for orographic clouds, which are related to the time it takes a parcel of air to condense to form supercooled liquid water and ice crystals while ascending to the mountain crest.

Missing in this discussion is the time that ice forms in orographic clouds after the leading edge forms as a droplet cloud. Ice particles have been shown to form a short distance downwind at surprisingly high temperatures as reported by Auer et al (1969u), Cooper and Vali (1981u).  

What then is the effect of introducing ice by AgI at an upwind edge where ice is already going to form immediately downwind in those situations?  Does this case represent a productive seeding possibility?  This scenario should have been discussed by the Chapter 8 authors.

The special case described here of non-precipitating clouds, where cloud seeding will be effective without question is not quantified.  How often do they occur, and how thick are they?  What is their cloud top temperature?  Are bases low enough so that the light, seeding-induced snowfall will reach the ground?  Will it be enough to justify the cost of seeding, by ground or aircraft?

The Chapter 8 authors were not aware of Rangno (1986u) who displayed the rapid changes in cloud characteristics that made seeding even orographic clouds problematic due to those changes in cloud top temperatures and in wind directions over periods of just 3-4 hours.

So many questions, so few answers by the authors, elements that point to the extreme difficulty of proper reviews in any field in meteorology!

If winds are weak, then there may be sufficient time for natural precipitation processes to occur efficiently. Stronger winds may not allow efficient natural precipitation processes but seeding may speed up precipitation formation. Stronger winds may not provide enough time for seeded icecrystals to grow to precipitation before being blown over the mountain crest and evaporating in the sinking sub saturated air to the lee of the mountain. A time window related to the ambient winds, however, is much easier to assess in a field setting than the time window in cumulus clouds.

The landmark randomized cloud seeding experiments at Climax, near Fremont Pass, Colorado (referred to as Climax I and Climax II), Colorado, reported by Grant and Mielke(1967) and Mielke et al.( 1970,1971) suggested increases in precipitation of 50% and more on favorable days (e.g. Grant and Mielke 1967; Mielke et al. 1970,1971), and the results were widely viewed as demonstrating the efficacy of cloud seeding (e.g. NRC 1973; Sax et al. 1975; Tukey et al. l978a, b; American Meteorological Society 1984),even by those most skeptical of cloud seeding claims(e.g. Mason 1980,1982). Nonetheless, Hobbs and Rangno (1979), Rangno and Hobbs (1987, 1993) question both the randomization techniques and the quality of data collected during those experiments and conclude that the Climax II experiment failed to confirm that precipitation can be increased by cloud seeding in the Colorado Rockies.

It appears that these cited critical papers by the present writer were not read by the authors of this review.  Hobbs and Rangno (1979), a study originated and carried out by the second author, demonstrated that the claims about a physical foundation for the Climax experiments were bogus.  These important findings was left out of the discussion above.   The experimenters had claimed out of thin air (Grant and Mielke 1967) that the stratifications by 500 mb temperatures were reliably connected to cloud top ones.

Moreover, the precipitation per day (PPD) does not decrease at Climax (or elsewhere in the Rockies) after a 500 mb temperature of -20°C is exceeded as the experimenters claimed (e.g., Grant et al. 1969u, 1974u, Chappell 1970u).  Rather, the PPD continues to increase at temperatures above -20°C as shown in Rangno 1979, Hobbs and Rangno (1979).   The decrease in PPD that occurred during Climax I when the 500 mb temperature was >-20° C was indicative of a bias in the draw on the Climax I control days rather than representative of PPD climatology. 

Hobbs and Rangno (1979) further demonstrated that the master’s thesis repeatedly invoked by the experimenters in support of the 500 mb/cloud top temperature correspondence claim (e.g., Grant and Elliott 1974) did no such thing,  but rather proved just the opposite.  This was due to the way that meteorological data were assigned to experimental days by the experimenters (i. e., as described by Fritsch in Grant et al. 1974u).   Critical papers were not read by the authors.  Q. E. D.

Quoting the authors from their paragraph above:  “the quality of the data collected during those experiments”.

This is a euphemism for what Rangno and Hobbs (1987) found.

The experimenters repeatedly described the NOAA-maintained recording gauge in the center of the Climax target as “independently” collected data (e.g., Mielke et al. 1970).  Rangno and Hobbs simply went to the NOAA hourly precipitation data publication for Colorado and used those data to evaluate the Climax experiments. Those published data were not the same as those used by the experimenters. 

The experimenters had, in fact, reduced the recording charts at that key gauge in Climax II themselves as revealed by Mielke 1995, and in doing so, helped the seeded day cases (Rangno and Hobbs 1987).  Climax II, not so lucky in its storm draw on seeded days as Climax I, was plagued by “helpful” errors.  Thirty-two of 43 differences in precipitation between that used by the experimenters and that in the NOAA publication helped the seeded cases.  The chance that such results came from an unbiased source can be rejected at a P value of 0.0001.

Climax I, however, benefitting from a storm draw on seeded days that favored the appearance of a cloud seeding effect in its first half of conduct,  had virtually no errors in data.

What do we make of this?  Circle the wagons? 

Or come to a logical conclusion that someone helped the Climax experiment replicate Climax II?  At this time, mid-way through Climax II, the Bureau of Reclamation’s cloud seeding division had begun spending hundreds of thousands of dollars on the planning of the Colorado River Basin Pilot Project.  There was, therefore, enormous pressure on the experimenters to have Climax II replicate Climax I.  

We let the reader decide what may have happened.


Inexplicably, the authors of this chapter omit the reanalysis of Mielke et al. (1981) by Rhea (1983u).  Indeed, this author’s own independent reanalysis of the Climax experiments (rejected in 1983) was partially because reviewers’ thought Rhea’s reanalysis, simultaneously under review and that came to the same result, was more robust.  Rhea showed that the mismatch between the time the control gauges were read and when the Climax target gauges were read resulted in the false impression that Climax II had replicated Climax I.  When the gauges were synchronized by Rhea (1983u), the Climax II seeding increases disappeared (as they also did using the published NOAA data in Rangno and Hobbs (1987).

A background note:  Grant et al. 1983u, however, strongly criticized the Rhea reanalysis before it was published.  Rhea altered his reanalysis along the lines suggested by Grant et al. prior to publication.  Nevertheless, Grant et al. did not revise their published comment to account for Rhea’s revisions.  Grant, in a personal note to Rhea at that time, did not know why he and his group had not altered their criticism of Rhea’s revised manuscript.

The published record concerning Rhea’s reanalysis is, therefore confusing; the experimenters appeared to critique Rhea’s paper while not actually doing so.

Even so, in their reanalysis, Rangno and Hobbs(1993) did show that precipitation increased by about 10% in the combined Climax I and II experiments.

First, the so-called “10% increase in precipitation for all of the Climax I and II experiments was “built in” by the choice of control stations mid-way through Climax I by the experimenters  as demonstrated in Rangno and Hobbs (1993).   We are sure the authors did not read that 1993 paper.  Control stations should have been selected prior to the Climax I experiment as good design demands.  Otherwise, the temptation to cherry-pick control stations that prove what the experimenters already believe becomes too big a temptation and that is surely what happened in Climax I at the half-way point.

If the seeding effect is real, it will continue following a cherry-picked group of control stations.  If there is no further sign of seeding, as shown in “Climax 1B,” the second half of Climax I by Rangno and Hobbs (1993) then we know that the gauges were picked because it showed what the experimenters believed before the experiment even began.  The lack of any sign of an effect of cloud seeding on precipitation continued through all of Climax II as well (Rangno and Hobbs 1993).

Finally, 1000 re-randomizations of the Climax data performed by the University Washington Academic Computer Center by Irina Gorodnoskya (unpublished data) showed that the 10% claimed increase in precipitation by the authors above was in the noise of these experiments.  It should not be quoted as an increase in snow due to seeding as the authors do here.

This should be compared, however, to the original analyses by Grant and Mielke (1967), Grant and Kahan (1974), Grant and Elliott (1974), Mielke et al. (1971), Mielke et al. (1976) and Mielke et al. (1981) that indicated greater than 100% increase in precipitation on seeded days for Climax I and 24% for Climax II.

Two other randomized orographic cloud seeing experiments, the Lake Almanor Experiment (Mooney and Lunn 1969) and the Bridger Range Experiment (BRE) as reported by Super and Heimbach (1983) and Super (1986) suggested positive results.

Of concern is that the “cold westerly” case in Phase I of the Lake Almanor experiment, where large seeding effects were reported was not reported in Phase II (Bartlett et al. 1975).   Also, the large increases (40%) in snow  reported in Phase I for cold westerly cases, is suspect since such clouds are likely to develop high natural ice particle concentrations naturally.  The Lake Almanor Phase I  is badly in need of a reanalysis by external skeptics;  its results should not be taken at face value.

 However, these particular experiments used high elevation AgJ generators, which increase the chance that the Agl plumes get into the supercooled clouds. Moreover, both experiments providedphysical measurements that support the statistical results (Super and Heimbach 1983, 1988).

There have been a few attempts to use mesoscale models to evaluate cloud seeding programs. Cottonet al. (2006) applied the Colorado State University Regional Atmospheric Modeling System(RAMS)to thesimulation of operational cloud seeding in the central Colorado Mountains in the 2003-2004 winterseason. The model included explicit representation of surface generator production of Agl at thelocations, burn rates, and times supplied by the seeding operator. Moreover, the model explicitlyrepresented the transport and diffusion of the seeding material, its activation, growth of icecrystals and snow,and precipitation to the surface. Detailed evaluation of model forecast orographicprecipitation was performed for 30 selected operational seeding days. It was shown that the model could be a useful forecasting aid in support of the seeding operations. But the model over-predictednatural precipitation, particularly on moist southwest flow days. The model also exhibited virtually no enhancement in precipitation due to glaciogenic seeding. There are a number of possiblecauses for the lack of response to seeding, such as over prediction of natural precipitation, which prevented the effects of seeding from being seen. In addition, the background CCN and INconcentrations are unknown, therefore lower CCN concentrations than occurred would make the cloudsmore efficient in precipitation production, thus reducing seeding effectiveness.

Finally, Ryan and King(1997) reviewed over 14 cloud seeding experiments covering much of southeastern, western,and central Australia, as well as the island of Tasmania. They concluded that static seeding over the plains of Australia is not effective. They argue that for orographic stratiform clouds, there is strong statistical evidence that cloud seeding increased rainfall, perhaps by as much as 30% over Tasmania when cloud top temperatures are between -10 and -l2°C in southwesterly airflow. The evidence that cloud seeding had similar effects in orographic clouds overthe mainland of southeastern Australia is much weaker. Note that the Tasmanian experiment had bothstrong statistical and physical measurement components and thus meets, or at least comes close to meeting, the NRC (2003) criteria for scientific “proof.” Cost/benefit analysis ofthe Tasmanian experiments suggests that seeding has a gain of about 13:1. This is viewed as a real gain to hydrologic energy production.

A complication revealed in the analysis of some of the Australian seeding experiments is thatprecipitation increases were inferred one to three weeks following seeding in several seedingprojects(e.g. Bigg and Turton 1988). Bigg and Turton ( I988) and Bigg ( 1988, 1990, 1995) suggestedthat silver iodide seeding can trigger biogenic production of additional ice nuclei. The latter research suggests that fields sprayed with silver iodide release secondary ice nuclei particles at intervals of up to ten days.

In summary, the “static” mode of cloud seeding has been shown to cause the expected alterations incloud microstructure including increased concentra­ tions of ice crystals, reductions of supercooled liquid water content, and more rapid production of precipitation elements in both cumuli (Isaac et al.1982; Cooper and Lawson 1984)and orographic clouds(Reynolds and Dennis 1986; Reynolds 1988;Super andBoe 1988; Super et al. 1988; Super and Heimbach 1988). The documentation of increases in precipitation on the ground due to static seeding of cumuli, however, has been far more elusive, with the Israeli experiment (Gagin and Neumann 1981) providing the strongest evidence that static seeding of cold-based, continental cumuli can cause significant increases of precipitation on the ground.  

Tukey et al. (1978b, Appendendix C, pC.1) wrote:   “The strongest evidence for rainfall enhancement involving the seven latest substantial experiments this task force has studied seems today to be that from the two Israeli experiments….”  The statement in blue (highlighted by this writer) which is almost the exact wording as that found in Turkey et al. (1978b) 30 years before the Springer book was published) is troubling indeed.    The assessment by Turkey et al. in 1978 was valid; it was not valid 30 years later when so much water has gone under the bridge concerning the Israeli cloud seeding experiments (or,  “too little water” due to cloud seeding).

Moreover,  citing Gagin and Neumann (1981) in 2009 as the strongest evidence in support of cloud seeding as they do,  demonstrated that the authors of this review were not aware of,  nor understood the literature in the topic they are supposedly reviewing.  The omission of critical literature by the authors as was proof of this assertion.

Why wasn’t I asked to review this manuscript in advance of publication since I am well-known as an expert on both the Colorado and Israel clouds, weather, and cloud seeding experiments?  Moreover, the authors of this review knew this.

The evidence that orographic clouds can cause significant increases in snowpack is far more compelling, particularly in the more continental and cold-based orographic clouds (Mielke et al. 1981; Super and Heimbach 1988).

The authors omit Rhea’s 1983u reanalysis of Mielke et al. 1981 and that of Rangno and Hobbs (1987) in remarking that “significant increases in snowpack” have been compellingly shown by Mielke et al. 1981.

Update to the orographic seeding claim above by the authors:  The NCAR Wyoming experiment, completed in 2013 (Rasmussen et al. 2018u), could find no viable evidence that seeding from ground generators had increased precipitation after six seasons of randomized seeding.

Perhaps, however, the most challenging obstacle to evaluating cloud seeding experiments to enhance precipitation, is the inherent natural variability of precipitation in space and time, and the inability to increase precipitation amounts to better than ~10%. This last obstacle puts great demands on the measuring accuracy and the duration of the experiments. Shouldn’t we expect similar obstacles in evaluating inadvertent effects of IN pollution on precipitation?

A well-stated description of the problem.


 List of references mentioned in the critical review that were uncited by the authors, or are relevant papers for an enhancement of Chapter 8 that were unavailable to these authors because they were published after Chapter 8 appeared.

Alpert, P., N. Halfon, and Z. Levin, 2008: Does air pollution really suppress precipitation in Israel?  J. Appl. Meteor. Climatology, 47, 943-948.

Alpert, P., N. Halfon, and Z. Levin, 2009:  Reply to Givati and Rosenfeld.  J. Appl. Meteor. Climatology, 48, 1751-1754.

Auer, A. H., D. L. Veal, and J. D. Marwitz, 1969: Observations of ice crystals and ice nuclei observations in stable cap clouds.  J. Atmos. Sci., 26, 1342-1343.

Ayers, G., and Levin, 2009:  Air pollution and precipitation.  In Clouds in the Perturbed Climate System.  Their Relationship to Energy Balance, Atmospheric Dynamics, and Precipitation. J. Heintzenberg and R. J. Charlson, Eds.  MIT Press, 369-399.

Bartlett, J. P., M. L. Mooney, and W. L. Scott, 1975:  Lake Almanor Cloud Seeding Program.  Preprint, Weather Modification Conference, San Francisco, 106-110.

Benjamini, Y, A. Givati, P. Khain, Y. Levi, D. Rosenfeld, U. Shamir, A. Siegel, A. Zipori, B. Ziv, and D. M. Steinberg, 2023:  The Israel 4 Cloud Seeding Experiment: Primary Results.   J. Appl. Meteor. Climate, 62, 317-327.

Chappell, C. F.,  1970:  Modification of cold orographic clouds.  Atmos. Sci. Paper No. 173, Dept. of Atmos. Sci., Colorado State University, Fort Collins, 196pp.

Cooper, W. A., and C. P. R. Saunders, 1980:  Winter storms over the San Juan mountains.  Part II:  Microphysical processes.  J. Appl. Meteor., 19, 927-941.

Cooper, W. A., and G. Vali, 1981:  The origin of ice in mountain cap clouds.  J. Atmos. Sci., 38, 1244-1259.

Dennis, A. S., 1989: Editorial to the A. Gagin Memorial Issue of the J. Appl. Meteor., 28, 1013.  No doi.

Gabriel, K. R., and Y. Neumann, 1978:  A note of explanation on the 1961–67 Israeli rainfall stimulation experiment.  J. Appl. Meteor., 17, 552–556.

Gabriel, K. R., and Rosenfeld, D., 1990: The second Israeli rainfall stimulation experiment: analysis of precipitation on both targets. J. Appl. Meteor., 29, 1055-1067.;2

Grant, L. O., DeMott, P. J., and R. M. Rauber, 1982:  An inventory of ice crystal concentrations in a series of stable orographic storms.  Preprints, Conf. Cloud Phys., Chicago, Amer. Meteor. Soc. Boston, MA. 584-587. No doi.

Grant, L. O., J. G. Medina, and P. W. Mielke, Jr., 1983:  Reply to Rhea. J. Climate Appl. Meteor., 22, 1482–1484.

Grant, L. O., C. F. Chappell, L. W. Crow, J. M. Fritsch, and P. W. Mielke, Jr., 1974:  Weather modification: A pilot project.  Final Report to the Bureau of Reclamation, Contract 14-06-D-6467, Colorado State University, 98 pp. plus appendices.

Grant, L. O., Chappell, C. F., Crow, L. W., Mielke, P. W., Jr., Rasmussen, J. L., Shobe, W. E., Stockwell, H., and R. A. Wykstra, 1969:  An operational adaptation program of weather modification for the Colorado River basin.  Interim report to the Bureau of Reclamation, Department of Atmospheric Sciences, Colorado State University, Fort Collins, 98pp.  (Available from the Bureau of Reclamation, Library,   Federal Building, Denver, Colorado 80302.

Halfon, N., Z. Levin, P. Alpert, 2009:  Temporal rainfall fluctuations in Israel and their possible link to urban and air pollution effects.  Environ, Res. Lett., 4, 12pp. doi:10.1088/1748-9326/4/2/025001

Kessler, A., A. Cohen, D. Sharon, 2003:  Analysis of the cloud seeding in Northern Israel.  Interim report submitted to the Israel Hydrology Institute and the Israel Water Management of the Ministry of Infrastructure.

Levin, Z., N. Halfon, and P. Alpert, 2010: Reassessment of rain enhancement experiments and operations in Israel including synoptic considerations.  Atmos. Res., 97, 513-525.


Levin, Z., N. Halfon, and P. Alpert: 2011:  Reply to the Comment by Ben-Zvi on the paper “Reassessment of rain experiments and operations in Israel including synoptic considerations” Atmos. Res., 99, 593-596.

Mielke, P. W., Jr., 1995:  Comments on the Climax I and II experiments including replies to Rangno and Hobbs.  J. Appl. Meteor., 34, 1228–1232.

National Research Council, 1973: Weather & Climate Modification: Progress and Problems. National Academy of Sciences, 258 pp.,

Neumann, J., K. R. Gabriel, and A. Gagin, 1967: Cloud seeding and cloud physics in Israel:  results and problems.  Proc. Intern. Conf. on Water for Peace.  Water for Peace, Vol. 2, 375-388.  No doi.

Rangno, A. L., 1979:  A reanalysis of the Wolf Creek Pass cloud seeding experiment.   J. Appl. Meteor., 18, 579–605.

Rangno, A. L., 1986:  How good are our conceptual models of orographic clouds?  In Precipitation Enhancement–A Scientific Challenge, R. R. Braham, Jr., Ed., Meteor. Monographs, 43, Amer. Meteor. Soc., 115-124. Invited paper, title assigned by A. S. Dennis.

Rangno, A. L., 1988: Rain from clouds with tops warmer than -10 C in Israel.  Quart J. Roy. Meteor. Soc., 114, 495-513.


Rasmussen, R. M., S. A. Tessendorf, L. Xue, C. Weeks, K. Ikeda, S. Landolt, D. Breed, T. Deshler, and B. Lawrence, 2018:  Evaluation of the Wyoming Weather Modification Pilot Project (WWMPP) using two approaches:  Traditional statistics and ensemble modeling.  J. Appl. Meteor. and Climate, 57, 2639-2660.

Rhea, J. O., 1983:  “Comments on ‘A statistical reanalysis of the replicated Climax I and II wintertime orographic cloud seeding experiments.'”  J. Climate Appl. Meteor., 22, 1475-1481.

Rosenfeld, D., 1998: The third Israeli randomized cloud seeding experiment in the south: evaluation of the results and review of all three experiments. Preprints, 14th Conf. on Planned and Inadvertent Wea. Modif., Everett, Amer. Meteor. Soc. 565-568. No doi.

Sharon, D., A. Kessler, A. Cohen, and E. Doveh, 2008:  The history and recent revision of Israel’s cloud seeding program.  Isr. J. Earth Sci., 57, 65-69.

Wurtele, Z. S., 1971: Analysis of the Israeli cloud seeding experiment by means of concomitant meteorological variables. J. Appl. Meteor., 10, 1185-1192.;2

Totality of References  in Chapter 8.1, “Introduction” through 8.2.2 “Seeding Winter Orographic Clouds” 


American Meteorological Society, 1984: Statement on planned and inadvertent weather modification.  Bull. Amer. Meteor. Soc., 66, 447–448.

Ben-Zvi, A., 1997:  Comments on “A new look at the Israeli randomized cloud seeding experiments.” J. Appl. Meteor., 36, 255-256.

Bigg, E. K., 1988: Secondary ice nucleus generation by silver iodide applied to the ground. J. Appl. Meteor., 27, 453-488.

Bigg, E. K., 1990:  Aerosol over the southern ocean. Atmos. Res., 25, 583-600.

Bigg , E. K., 1995:  Tests for persistent effects of cloud seeding in a recent Australian experiment.  J. Appl. Meteor., 34, 2406-2411.

Bigg, E. K., and E. Turton, 1988: Persistent effects of cloud seeding with silver iodide.  J. Appl. Meteor., 27, 505-514

Braham, Roscoe R., Jr., 1986:  Rainfall enhancement–a scientific challenge.  Rainfall Enhancement–A Scientific Challenge, Meteor. Monogr., 21, No. 43,  1–5.

Cooper, W. A., and R. P. Lawson, 1984:  Physical interpretation of results from the HIPLEX-1 experiment.  J. Climate Appl. Meteor., 23, 523-540.

Cotton, W. R., 1982: Modification of precipitation from warm clouds. A review.  Bull. Meteor. Soc., 63, 146-160.

Cotton, W. R., 1986a: Testing, implementation, and evolution of seeding concepts–a review.  In Precipitation Enhancement–A Scientific Challenge, R. R. Braham, Jr., Ed., Meteor. Monographs, 43, Amer. Meteor. Soc., 63-70.

Cotton, W. R., 1986b: Testing, implementation, and evolution of seeding concepts–a review.  In Precipitation Enhancement–A Scientific Challenge, R. R. Braham, Jr., Ed., Meteor. Monographs, 43, Amer. Meteor. Soc., 139-149.

Cotton, W. R., and R. A. Pielke, 1992:  Human Impacts on Weather and Climate. ASteR Press, 271pp.

Cotton, W. R., and R. A. Pielke, 1995:  Human Impacts on Weather and Climate, 1st edition, Cambridge University Press, 288pp.

Cotton, W. R., and R. A. Pielke, 2007:  Human Impacts on Weather and Climate, 2nd edition, Cambridge University Press, 308pp.

Cotton, W. R., R. R. McAnelly, G. Carrio, P. Mielke, and C. Hartzell, 2006:  Simulations of snowpack augmentation in the Colorado Rocky Mountains.  J. Weather Modification, 38, 58-65.

Dennis, A. S., 1980:  Weather Modification by Cloud Seeding.  Academic Press, 267pp.

Dennis A. S., and H. D. Orville, 1997: Comments on “A new look at tbe Israeli cloud seeding experiments.” J. Appl. Meteor., 36, 277-278

Gagin, A., 1986:  Evaluation of “static” and “dynamic” seeding concepts through analyses of Israeli II experiment and FACE-2 experiments.  In Rainfall Enhancement–A  Scientific Challenge, Meteor. Monogr., 43, Amer. Meteor. Soc., 63–70.

Gagin, A., and K. R. Gabriel, 1987:   Analysis of recording rain gauge data for the Israeli II experiment. Part I:  Effects of cloud seeding on the components of daily rainfall.  J. Climate Appl. Meteor.,  26,   913–926.

Gagin, A., and J. Neumann, 1974: Rain stimulation and cloud physics in Israel. Weather and Climate Modification, W. N. Hess, Ed., John Wiley and Sons,  454–494.

Gagin, A., and J. Neumann, 1981:  The second Israeli randomized cloud seeding experiment: evaluation of results.  J. Appl. Meteor., 20, 1301–1311.

Garstang, M., R. Bruintjes, R. Serafin, H. Oroville, B. Boe, W. R. Cotton, J, Warburton, 2005:  Weather Modification; Finding common ground. Bull. Amer. Meteor. Soc. 86, 647-655.

Givati, A., and Rosenfeld, D., 2005: Separation between cloud-seeding and air pollution effects. J. Appl. Meteor. Climate, 44, 1298-1314.

Grant, L. O., and R. D. Elliott, 1974:  The cloud seeding temperature window.  J. Appl. Meteor., 13, 355-363.

Grant, L. O., and A. M. Kahan, 1974:  Weather modification for augmenting orographic precipitation. Weather and Climate Modification, W. N. Hess, ed., John Wiley and Sons, 282-317.

Grant, L. O.,  and P. W. Mielke, Jr., 1967:  A randomized cloud seeding experiment at Climax, Colorado 1960-1965.  Proc. Fifth Berkeley Symposium on Mathematical Statistics and Probability, Vol. 5, University of California Press, 115-131.

Hobbs, P. V., , andA. L. Rangno, 1979:  Comments on the Climax randomized cloud seeding experiments.   J. Appl. Meteor., 18, 1233-1237.

Isaac, G. A., J. W. Strapp, and R. S. Schemenauer, 1982: Summer cumulus cloud seeding experiments near Yellowknife and Thunder Bay, Canada. J. Appl. Meteor., 21, 1266-1285.

Kerr, R. A., 1982: Cloud seeding: one success in 35 years.Science,217,519–522.

Levin, Z., E. Ganor, and V. Gladstein, 1996: The effects of desert particles coated with sulfate on rain formation in the eastern Mediterranean.  J. Appl. Meteor., 35, 1511-1523.;2

Levin, Z., A. Teller, E. Ganor, and Y. Yin, 2005: On the interaction of mineral dust, sea salt particles and clouds–A measurement and modeling study from the MEIDEX campaign.  J. Geosphys. Res.110, D20202, doi 10.1029/2005JD005810.

Mason, B. J., 1980:  A review of three long-term cloud-seeding experiments.  Meteor. Mag., 109, 335-344.

Mason, B. J.,, 1982:  Personal Reflections on 35 Years of Cloud Seeding.  Contemp. Phys., 23, 311-327.

Mielke, P. W., Jr., K. J. Berry, A. S. Dennis, P. L. Smith, J. R. Miller, Jr., B. A. Silverman, 1984: HIPLEX-1: Statistical evaluation. J. Appl. Clim. Meteor.23, 513-522.

Mielke, P. W., Jr., L. O. Grant, and C. F. Chappell, 1970:  Elevation and spatial variation effects of wintertime orographic cloud seeding.  J.  Appl. Meteor., 9, 476-488.  Corrigenda, 10,  842, 15, 801.

Mielke, P. W., Jr.,  L. O. Grant, and C. F. Chappell, 1971:  An independent replication of the Climax wintertime orographic cloud seeding experiment.  J. Appl. Meteor., 10, 1198-1212.

Mielke, P. W., Jr.,  G. W. Brier, L. O. Grant, G. J.  Mulvey, and P. N. Rosenweig, 1981:  A statistical reanalysis of the replicated Climax I and II wintertime orographic cloud seeding experiments.  J. Appl. Meteor., 20, 643-659.

Mielke et al. 1976 does not appear in the references of this volume.

Mooney, M. L., and G. W. Lunn, 1969: The area of maximum effect resulting form the Lake Almanor randomized cloud seeding experiment.   J. Appl. Meteor., 8, 68-74.

National Research Council-National Academy of Sciences, 1973:  Weather and Climate Modification: Progress and Problems, T. F. Malone, Ed., Government Printing Office, Washington, D. C., 258 pp.

National Research Council, 2003: Critical Issues in Weather Modification Research. National Academy Press, 123 pp.

Rangno, A L., and P. V. Hobbs, 1987:  A re-evaluation of the Climax cloud seeding experiments using NOAA published data.  J. Climate Appl. Meteor., 26,  757-762.

Rangno, A L., and P. V. Hobbs, 1993:  Further analyses of the Climax cloud-seeding experiments.  J. Appl. Meteor., 32, 1837-1847.

Rangno, A L., and P. V. Hobbs, 1993 (sic):  A new look at the Israeli cloud seeding experiments.  J. Appl. Meteor., 34, 1169-1193.

Rangno, A L., and P. V. Hobbs, 1997a: Reply to Woodley.  J. Appl. Meteor., 36, 253.

Rangno, A L., and P. V. Hobbs, 1997b: Reply to Ben-Zvi.  J. Appl. Meteor., 36, 257-259.

Rangno, A L., and P. V. Hobbs, 1997c:  Reply to Rosenfeld.  J. Appl. Meteor., 36, 272-276.

Rangno, A L., and P. V. Hobbs, 1997d: Reply to Dennis and Orville.  J. Appl. Meteor., 36, 279.

Rangno, A. L., and P. V. Hobbs, 1997e:  Comprehensive Reply to Rosenfeld, Cloud and Aerosol Research Group, Department of Atmospheric Sciences, University of Washington, 25pp, with a forward by P. V. Hobbs.

Reynolds, D. W., 1988: A report on winter snowpack-augmentation.  Bull Amer. Meteor. Soc., 69, 1290-1300.

Reynolds, D. W., and A. S. Dennis, 1986:  A review of the Sierra cooperative project. Bull. Amer. Meteor. Soc.67, 513-523.

Rosenfeld, D., 1997:  Comment on “Reanalysis of the Israeli Cloud Seeding Experiments”, J. Appl. Meteor., 36, 260-271.

Rosenfeld, D., Y. Rudich, and R. Lahav, 2001: Desert dust suppressing precipitation.  A possible desertification feedback loop.  Proc. Nat. Acad. Sci.98, 5975-5980.

Ryan, B. F., and W. D. King, 1997:  A critical review of the cloud seeding experience in Australia.  Bull. Amer. Meteor. Soc.78, 239-254.

Sax, R. I., S. A. Changnon, L. O. Grant, W. F. Hitchfield, P. V. Hobbs, A. M. Kahan, and J. S. Simpson, 1975 :Weather modification:  where are we now and where are we going?  An editorial overview.  J. Appl. Meteor.14, 652–672.

Schemenauer, R. S., and A. A. Tsonis, 1985:  Comments on “physical interpretation of results from the HIPLEX-1 experiment.  J. Appl. Meteor.24, 1269-1274.

Silverman, B. A., 1986:  Static mode seeding of summer cumuli-a review.  Rainfall Enhancement–A  Scientific Challenge, Meteor. Monogr., 21, No. 43,  Amer. Meteor. Soc., 7–24.

Silverman, B. A.., 2001. A critical assessment of glaciogenic seeding of convective clouds for rainfall enhancement. Bull. Am. Meteor. Soc., 82, 903-924.

Silverman, B. A., 2003: A critical assessment of hygroscopic seeding of convective clouds for rainfall enhancement. Bull. Am. Meteor. Soc., 84, 1219-1230.

Smith, P. L., A. S. Dennis, B. A. Silverman, A. B. Super, E. W. Holroyd, W. A. Cooper, P. W. Mielke, K. J. Berry, H. D. Orville, and J. R. Miller, 1984:  HIPLEX-1:  Experimental design and response variables. J. Clim. Appl. Meteor.23, 497-512.

Tukey, J. W., Jones, L. V., and D. R. Brillinger, 1978a:  The Management of Weather Resources, Vol. I,  Proposals for a National Policy and Program.  Report of the Statistical Task Force to the Weather Modification Advisory Board, Government Printing Office. 118pp.

Tukey, J. W., D. R. Brillinger, and L. V. Jones, 1978b:  Report of the Statistical Task Force to the Weather Modification Advisory Board, Vol. II.  U. S. Government Printing Office, pE-3.

Simpson, J. S., 1979:  Comment on “Field experimentation in weather modification.” J. Amer. Statist. Assoc., 74, 95-97.

Super, A. B., 1986: Further exploratory analysis of the Bridger Range winter cloud seeding experiment. J. Appl. Meteor,25, 1926-1933.

Super, A. B., and B. A. Boe, 1988: Microphysical effects of wintertime cloud seeding with silver iodide over the Rocky mountains.  Part III.  observations over the Grand Mesa, Colorado. J. Appl. Meteor., 27, 1166-1182.

Super, A. B., and J. A. Heimbach,1983:  Evaluation of the bridger range cloud seeding experiment using control gauges.  J. Appl. Meteor., 22, 1989-2011.

Super, A. B., and J. B. Heimbach, Jr., 1988:  Microphysical effects of wintertime cloud seeding with silver iodide over the Rocky mountains.  Part II.  Observations over the Bridger Range mountains.  J. Appl. Meteor., 27, 1152-1165.

Super, A. B., B. A. Boe, and E. W. Holroyd, 1988:  Microphysical effects of wintertime cloud seeding with silver iodide over the Rocky Mountains.  Part I.  Experimental design and instrumentation.  J. Appl. Meteor., 27, 1145-1151.

Woodley, W., 1997:  Comments on “A new look at the Israeli Randomized cloud seeding experiments.” J. Appl. Meteor., 36, 250-252.

Young, K. C., 1993:  Microphysical Processes in Clouds.  Oxford University Press, 335-336.

The Nightmare before Banff: A Science Coming Out Saga

The story of a coming out science “party” for a young, under-credentialed worker who has found that his greatest expertise is finding fault in the work of others.  But he now, for the first time, must defend his work overturning that of the leading scientists in his field  “at conference.”


  • Not a horror movie, but a science story that reveals the human element in science. Our protagonist is a shy, under credentialed weather forecaster who takes on the best scientists in their field but must pass through a frightening mental hoop before demonstrating at a conference that one of their published cloud seeding successes was illusory.  Well, I guess it could be a movie, one with a scary part…
  • This cloud and weather-centric protagonist has already taken the famous scientists on in the published literature in May 1979 when his first ever paper appeared in a journal reanalyzing one of their most important experiments.  But he must now defend his work in person at a large conference in Banff, Alberta, Canada, in October 1979.  This will be his first presentation at a scientific conference, his “coming out party.”
  • However, an advance program for the Banff conference is also published in May 1979 and it reveals that our protagonist’s findings will be addressed by the famous scientists right before he gets up to present them!   Colloquially, “WTF”?
  • In September 1979, he learns from his lab chief that the famous scientists are, indeed, working on a new analysis of the experiment that our protagonist will discuss at Banff.  Palpitations and dread levels rise.  He writes to the famous scientists inquiring about this new analysis of their experiment, but receives no reply.
  • Our protagonist lives a nightmare few months before the conference, wondering even if he should go and be humiliated as he expects.  He is not on a credential par with those scientists at any level.  He is just an ordinary meteorologist and weather forecaster with no advanced degree, one of the very few with only a bachelor’s degree presenting at the conference.
  • Our protagonist redoes his published paper, looking for errors he might have made, or ones that the reviewers might have missed, ones that will surely be emphasized at the conference.  He doesn’t find any.
  • He does go to the October conference filled with terrible dread anyway, bur his allies, the director of his group, and a supporting prof are with him.
  • Late in the afternoon before his presentation the next day, one of the famous scientists tells our protagonist that they won’t be discussing his paper after all before he gives it.  They acknowledge, behind the scenes, that they, “screwed up.”
  • The story ends on a happy note.  There is no criticism of his paper.
  • Our protagonist also realizes that his awful 1975 gaffe in a local newspaper story about the work of the famous scientists may have given them an understandable motive for some “payback” as the months of dread, intentional or not, seem now to have been.

Note:  There is some real bawling described in this saga by our protagonist concerning the journal publication hurdles that one must go through.  In his case, because his controversial work overturning the published research of others was done on his own initiative, “time and dime,” there is an awful lot of emotional “ownership” in what happens.

If you are now like I was  in this long ago,  “anxiety chapter” of my life, one that so many of our citizens are likely experiencing today due to so many unwise changes being foisted on our country, the war in the Middle East,  etc., I highly recommend this video on anxiety:



————-The Nightmare before Banff—————-

The program for the October 1979 Banff 7th Conference on Planned and Inadvertent Weather Modification came out in the Bulletin of the American Meteorological Society (BAMS) in May 1979.  My talk there was going to be a coming out party for me because it was going to be my first presentation at a conference.  Previously, I had just run a microphone around at a conference for those who had questions after a talk.  And I was going to present at a joint meeting of both the Planned and Inadvertent Weather Modification crowd, and the “Statistics in the Atmosphere” crowd, too; in other words, in front of a big audience of top scientists.  May 1979 was the same month that my peer-reviewed paper reanalyzing the Wolf Creek Pass experiment (WCPE) came out as the lead article in the J. Appl. Meteor.  That was the work I was going to summarize at Banff.

But what I saw in the May BAMS program for the October conference terrified me.  The famous leaders of the Colorado State University (CSU) cloud seeding experiments, Prof. Lewis O. Grant, and their statistician, Dr. Paul W. Mielke, Jr, were going to discuss my paper before I gave it!


Mielke and Grant were at the top of the mark in the world of cloud seeding/weather modification and had published several papers describing their prestigious cloud seeding successes at Climax and Wolf Creek Pass, Colorado.

I wondered, too, how the program organizers could allow this sequence.

I was going to be humiliated, I was sure, due to errors that I had made, but did not, or could not recognize due to my own bias or ignorance.   Maybe I had not even copied down runoff or precipitation data in my dozens of “pen and ink” spreadsheets correctly from the volumes of government published data, the source of my analyses.1

I had palpitations off and on from the time I read that BAMS program until the day before my talk at Banff.   I just could not imagine how horrible it was going to be; I repeatedly envisioned that my truly limited skills were going to be exposed. I was sure I would have nothing to say when I got up to speak after Professor Grant and Dr. Mielke had spoken and had surely decimated my reanalysis.  I would be standing there, I imagined, with my mouth open, maybe apologizing for errors.  It would be similar to that 3rd grade trauma with Ann Stone, a never forgotten humiliation!2

I would go to movies, “Serpico” comes to mind, and right in the middle, I would think about Banff, and my heart would seem to want to burst out of my chest, the palpitations were so strong.  I feel lucky I didn’t keel over during those months before Banff.  My heart is pounding right now and I am shivering as I flesh out this chapter of my life.  This must seem silly to more experienced people I suppose.

September 1st, 1979: dread increases. 

I learn from Prof. Peter Hobbs, the director of my group,  that a new analysis of the Wolf Creek Pass experiment is being worked up by the seeding experimenters at Colorado State University.  I write to their leader, Professor Lewis O. Grant, and ask him about the new analysis, but I get no reply.  Now I am positive all the faults that I missed in my paper will be shown up, that my presentation will be shown to be severely flawed and worthless before I give it!

I often thought, too, that I just wouldn’t go to Banff, though my allies at the University of Washington, Profs. Peter Hobbs and Lawrence F. Radke, were going, so that wasn’t really wasn’t an option.  Prof. Hobbs was also going to present my Colorado work that showed that there was no basis for the foundation of the CSU cloud seeding claims that supported huge increases in snow due to seeding when the 500 mb (hPa) temperatures were equal to or higher than -20°C, a temperature level that the experimenters had misperceived as ones that were a proxy  for cloud top temperatures.

Prof. Hobbs had reviewed my Wolf Creek Pass experiment (WCPE) manuscript drafts, too, when I started bringing them in from home, but he did not know how reliable my work was; Prof. Hobbs was a facilitator/editor of publications that originated within his group.  He also did not allow papers to go out from his group without his purview.  While improving drafts submitted to him, he usually became a co-author, and sometimes the lead author, as on Hobbs and Rangno (1978, a reanalysis of the Skagit Project) and again on Hobbs and Rangno (1979, “Comments on the Climax and Wolf Creek Pass Experiments”).

The WCPE was the third in a trifecta of cloud seeding successes reported by CSU scientists that formed an imposing edifice of cloud seeding successes.  They appeared to reinforce one another, and the Climax experiments had been specifically called out by our best scientists as cloud seeding successes (e.g., the National Academy of Sciences (NAS) in 1973, Warner 1974).  Prof. Hobbs had been a member of the NAS panel that had praised the CSU cloud seeding work and it was also cited in his popular 1977 graduate level book with Prof. J. M. Wallace, “Atmospheric Science:  An Introductory Survey.”

Moreover, the WCPE cloud seeding success, whose preliminary results were being presented to the Bureau of Reclamation’s cloud seeding division in 1969, was the reason why the massive Colorado River Basin Pilot Project (CRBPP) took place centered on Wolf Creek Pass.  Greater potential increases in snow due to cloud seeding were being reported by CSU scientists in the WCPE as a characteristic of storms in southwest Colorado in the San Juan Mountains than in northern Colorado where their highly regarded Climax randomized experiments had taken place.

The CRBPP remains as the nation’s costliest randomized orographic cloud seeding experiment.   In my opinion, the Bureau of Reclamation made many efforts to “do it right” by randomizing it, having others who did not know the if a random decision had been called, measure the precipitation each day.

Prior to carrying out the reanalysis of the WCPE, I had been a forecaster with the CRBPP for all its operating winters from 1970/71 through 1974/75, the only meteorologist to have been with it the whole time.  I had been, Acting Project Forecaster during its first season following the departure of Project Manager, Paul T. Willis, and Assistant Project forecaster for the remaining seasons.  I drew the morning and evening weather maps3and made forecasts five days a week as Assistant forecaster, and seven days a week as Acting Project Forecaster for most of the 1970/71 season.[2]  Namely, I had something to do with most of the random calls for an “experimental day” in the CRBPP.

I knew I had to go to Banff or forever be noted as a coward and take whatever Professors Grant and Mielke delivered no matter how humiliated I might be.


There were no personal computers in those days of the mid-1970s, of course; I was using a $100 Texas Instrument handheld calculator for statistics and correlations from the dozens of pen-and-ink spreadsheets9 I had made copying raw data from the CRBPP, runoffs from geological survey books, and from NOAA Climatological Data and Hourly Data publications.  Sometimes I would have to enter a pair of numbers to get correlations three times if the second one didn’t produce the same result as the first cycle.  That, too, was a nightmare and so frustrating when it happened.

Due to that May 1979 program in BAMS, I redid the whole WCPE published paper from scratch thinking there must be a serious problem.  I didn’t find one, but still, I thought, SOMETHING must be wrong with it and I was going to hear about it at Banff!


Some regrettable, necessary background that might have contributed to the BAMS program sequence I saw: payback?

A careless and inappropriate metaphor that I said to a newspaper reporter at the end of a recorded interview became a secondary headline in the Durango Herald newspaper in November 19754:

Cloud Seeding… Rangno:  ‘Watergate of Meteorology.’”

Since Watergate was a burglary by political actors, I had carelessly implied criminal activity had taken place in the reporting of CSU’s cloud seeding work!  Yikes!

What I had meant was that if the CSU work was overturned it would be a “big deal” since it had led to the funding of the massive CRBPP.  Watergate was on everyone’s mind in 1975, and what I said just came out without a lot of thought.

The reporter, Mike McRae for the Durango Herald, and who had told me after our long interview that I could review his article before it came out, canceled my pre-pub review the evening before, saying, “Trust me,  Art.”

I left for Fresno, California, the next day for short term employment with Atmospherics, Inc., a cloud seeding company, and did not see the Herald article until a week after it appeared.  It was sent to me by a Durango friend and E. G.&G., Inc., co-worker.

I couldn’t sleep after I saw it.

How that Durango newspaper headline happened: a cautionary tale for young scientists who might deal with the press. 

The reporter who recorded my November 1975 interview within the confines of the Durango Herald offices told me I would get to review his article before it appeared, an unusual offer.  I wanted to make sure that what I told him was accurately portrayed.  I had been cautious in what I said, and that was reflected in the full article.

However, the evening before it was to appear and a day on which I was traveling to Fresno, California, the reporter, Mike McRae, called to say that I wouldn’t be able to review his writeup beforehand after all.  He assured me it would fine with those magic words: “Trust me, Art.”

But after I saw it in Fresno, I couldn’t sleep, as you would imagine.  The body of the piece was accurate, but that secondary headline; oh my.  I was expecting to hear from CSU lawyers at any time!5

Why was I interviewed in the first place? 

I had previously written a critical piece concerning the obstacles to successful cloud seeding that were encountered during the CRBPP that perhaps McRae had seen in the spring of 1974 in a Telluride, CO, magazine, the Deep Creek Review.  Unknowingly, the reporter was also setting me up for publication of two contrasting views of cloud seeding; mine and the CRBPP Project Manager, Mr. Larry Hjermstad, a seeding partisan who went on to form a very successful cloud seeding company in Colorado, Western Weather Consultants.

I had no problem with the idea of, “contrasting views” when I saw the paper.  It’s what the public should see so that they can take the best path forward when there are questions about something.

Those nationally recognized CSU experiments, lauded by our best individual scientists and the National Academy of Sciences[3] itself, had led to the multi-million-dollar CRBPP, still the mostly costly such mountain cloud seeding experiment ever undertaken ($40-50 million in 2020 dollars).  So, in fact, it would be a scientific story of great magnitude if the CSU cloud seeding successes reported on many occasions in peer-reviewed journals, were illusory.

When I was interviewed in November 1975, the CRBPP had ended in the spring of 1975 without proving cloud seeding had increased snowfall.  It had been widely expected beforehand that the CRBPP would confirm the CSU results with as much as 50% increases in snowfall on seeded days and something like 250,000 additional acre-feet of runoff even though it had been randomized.

But instead of questioning the validity of the successes on which the CRBPP was based, it was believed, and published in the journal literature on several occasions, that it was the conduct of the CRBPP as well as design flaws that caused it to fail.  It was an odd interpretation to me due to the discrepancies in the CSU hypotheses revealed during the CRBPP.

However, blaming the faulty conduct of the CRBPP did remove blame from the sponsor of the CRBPP, the Bureau of Reclamation’s cloud seeding division, and the reviewers of those faulty manuscripts that allowed ersatz claims of great cloud seeding successes to reach the peer-reviewed journals in the first place.

When I next saw “Mike the Reporter” in a Durango supermarket, he advised me, “Never trust a newspaper reporter.”

Q. E. D.


Consequences of the 1975 Durango Herald article

Mike McCrae’s story was to have a major impact at CSU and was to save me a lot of work (at least for a while).  The story reached the National Science Foundation that had partially funded the prior cloud seeding experiments by CSU scientists.   They wanted to know from them, “What’s going on?”6

Moreover, I had stated in the Durango Herald article that I was going to reanalyze ALL three of the major CSU cloud seeding experiments!  What was I thinking?  I had no idea how much work that was going to be.  I just felt something had to be done by someone, even if it was by an under-credentialed weather forecaster.  But, I “knew the territory” and the weather patterns as a forecaster virtually like no one else.  And it was becoming clear that the ”narrative” for the failed CRBPP was design flaws and poor execution on the part of the E. G. & G., Inc. seeding team that I was a part of.

CSU scientists, perhaps concerned over an outsider reevaluating their experiments, beat me to it.

The Apology and Request for Data from Colo State University

After returning from Fresno, California in early December 1975, I drove to CSU to apologize in person for my newspaper gaffe to Prof. Lewis O. Grant, leader of the CSU seeding experiments. But I also went there to obtain data from their cloud seeding experiment at Wolf Creek Pass.  I had come to believe it was suspect as a success due to the many discrepancies and obstacles to cloud seeding that were encountered during the CRBPP.

Prof. Grant was extremely gracious in our meeting in accepting my apology and supplied the data I requested; he was that kind of guy.

Updating Prof. Lewis O. Grant on my reanalysis

 During the winter of 1975/76 and after my visit to CSU, I remained in Durango to work on the reanalysis of the WCPE, living off my savings (no skiing!).   I passed Prof. Lewis O. Grant, progress reports as I moved along on my reanalysis over the following two years. I had promised him I would do this when I met with him in December 1975 in exchange for the CSU data.

He was actually encouraging me as I forwarded my “progress” reports to him—yes, again, he was that kind of guy.  Prof. Grant wrote at one point that I had found “something important” as the WCPE unraveled.   But after a while he stopped responding to my reports and I stopped sending them.

1976:  Joining Peter Hobbs’ Cloud Physics Group

By September 1976, after that self-funded “sabbatical” in Durango during the winter of 75/76, I had been hired by Prof. Peter V. Hobbs to be a part of his “Cloud Physics Group” at the University of Washington when a member of his airborne research group left.7

I had called Prof. Larry Radke in his group in August 1976 about the Cloud Physics Group’s airborne study in Durango that had taken place during the spring of 1974.  Prof. Radke informed me that there was a job opening in Prof. Hobbs group and, “Was I interested in applying for it?”  I was, and I was interviewed over the phone by Prof. Hobbs soon afterwards and got hired!

In August I was hired into his group as a “Flight Meteorologist” taking the place of Mr. Don Atkinson who had resigned to go back to school.  I also had an offer from Atmospherics, Inc., to work more short-term cloud seeding programs for them around the world.

I took the offer from Prof. Hobbs.

I wasn’t sure I was skilled enough to be in academia under a world class scientist like Prof. Hobbs.  I wasn’t sure, either, how I would do flying in their 1939 manufactured B-23 research aircraft.  I had been on one of their flights during their 1974 research project in Durango and, surprisingly,  didn’t get motion sickness.

I started at the University of Washington in mid-September 1976, and continued to work with the data of the Wolf Creek Pass experiment at home and on my own time at the UW.  Prof. Hobbs, ebullient about cloud seeding at the time I arrived due to just having finished the successful “Cascade Project,” a non-randomized seeding experiment, took a great interest in the drafts of manuscripts I began to bring in, editing them and revamping them, namely, using his great skills to improve my drafts.

Prof. Hobbs had just been a member of the National Academy of Sciences (1973) and in composing their optimistic report on the Climax, CO, experiments, had written a similar optimistic, “Personal Viewpoint” in 1975 in Sax et al.’s review of weather modification in the J. Appl. Meteor.

Banff:  The Nightmare Ends

In a hallway of the convention center in Banff where the talks were going to be given, I ran across Prof. Grant coming my way the evening before my talk.  He said, “Art, I’m not even going to talk about Wolf Creek.”  I was relieved but wasn’t sure what was going to happen.  I still don’t know why Prof. Grant or Dr. Mielke didn’t tell me this months or weeks in advance.  I was their nemesis, of course, and maybe it was as simple as that. Or, maybe I was being punished for the awful Durango Herald headline?  Who could blame them?

The next day despite what Prof. Grant had said, I was so nervous and sweating before my talk, that I grabbed a can of deodorant and sprayed my hair and forehead with it by accident before walking over to give it.  I thought I had grabbed a can of hairspray!

I opened my talk by telling the 300 or so scientists in the “joint meeting” audience that Wednesday about what I had done due to my nerves, spontaneously using it as my intro at this, my first conference presentation.  I followed this with a quip, “At least now my forehead won’t sweat.”  It got a good laugh, I relaxed some, and got through the 10 min talk that had caused so much stress beforehand.

I ended my talk on what I hoped was a conciliatory note: “Who wouldn’t have believed that all this wasn’t due to cloud seeding?”, referring to the large runoff anomalies of the three seeded seasons of the WCPE reported by Grant et al. 1969, later by Morel-Seytoux and Saheli (1973).  The chances that they were due to natural causes could be rejected with a 99% confidence level (the same level as the Skagit Project that was also misperceived as a cloud seeding success).

But, soberingly enough, it was beyond a doubt that natural storm factors are what had created those WCPE runoff anomalies that looked so much like the result of cloud seeding.  The key mistake by the experimenters in both the WCPE and the Skagit project s was NOT declaring controls in advance of operations.

It was at this meeting that Dr. Paul Mielke, Jr., told me later that, “we screwed up.”  What a terrific guy he was to say that!

Banff ended on a high note.  I often think how horrible it would have been if I had, indeed, “chickened out” due to the recurring fear I had after the Banff program came out.

October 1979:  All that the CRBPP had been based on was gone after Banff

 Retraction of the of the key Climax, CO, randomized wintertime cloud seeding successes first appeared in March 1979 (J. Amer. Stat. Assoc. by Prof. P. W. Mielke, Jr.); the results appeared to be part of a statewide pattern and not localized to Climax.   The results were verbally retracted by J. O. Rhea at Banff in October 1979.8  This occurred after so-called “downwind” increases in snowfall on the same days as seeding had seemed to have increased snow so much at Climax were found to be due to a natural bias.  Upslope winds that favored more snow on seeded days at downwind locations from Climax were more prevalent on those days (Meltesen et al. 1978) compromising the downwind seeding claims.

So, within six months in 1979, March through October, all that the CRBPP had been based on, which included my WCPE reanalysis published in May, was gone!   It can be argued that Mike McRae’s 1975 article set off a major chain reaction.

It was regrettable that the 1979 Banff program summary by Semonin and Hill, finally published in 1981 in BAMS, failed to acknowledge the historic retractions, or the critical unreliability of the Climax experimenters’ claims about cloud top temperatures that was presented by Prof. Hobbs.  Perhaps Semonin and Hill did not actually attend the conference?  Or forgot what had taken place?

However, Semonin and Hill, while missing those key elements, did take note of the historic “leafletting” of conference attendees by the CSU experimenters.  In their leaflet they claimed that the Hobbs and Rangno (1979) critique of the foundations of the CSU experiments got it wrong and defended their work. This is the only conference that I know of in which pre-session conflictive leafletting has been conducted.

The emotions surrounding journal work done on your own time and initiative

I am guessing that many young scientists, excited about their work, have had this experience with their first manuscript.

The manuscript of the WCPE reanalysis was sent out in March 1978, almost two and a half years after I began working on it in November 1975.  Prof. Peter Hobbs took a great interest in my unfunded work once I arrived in his group and told him about it after I was hired in September 1976.

Prof. Hobbs did not permit articles to be submitted to journals from members of his group without his going over them.  Due to Prof. Hobbs experience and editorial gifts, the drafts I brought in from home were steadily improved.

I had even done my own drafting of all of the 21 figures in the WCPE reanalysis, to give you an idea of the magnitude of this overall effort that I was so bonded to.  Here’s an example of one I did from the 1979 WCPE reanalysis publication:

As anyone could imagine, doing your own research, drafting your own figures, brings more “ownership” and emotional attachment than might be the case with funded research. This became only too clear when the long-awaited reviews of my reanalysis of the WCPE came back in a manila envelope in August 1978, sent from Dr. Bernard A. Silverman, the editor for this manuscript for the Amer. Meteor. Soc.’s Journal of Applied Meteorology.

It took me a week to open that envelope.  More palpitations; would my manuscript be rejected or accepted?

Eventually, I opened it and read the first review that Dr. Silverman had placed on the top of what turned out to be three reviewers’ assessments of my manuscript.

That first reviewer recommended, “reject.”

The reviewer had written that I had no business doing a reanalysis of the CSU work; I didn’t have the background to do it and the paper should be rejected.  There was no real criticism of the contents of my manuscript. Nevertheless, I wept uncontrollably, shaking; I was going to fail in my monumental effort.

That “reject” reviewer was only too correct concerning my lack of a technical background to do what I had tried to do. But it was also clear to me after several years after 1975, that a better credentialed researcher was not going to be looking into the original CSU experiments the massive CRBPP had been based on.   That would have been risky.   It was much better for all involved to walk away from the CRBPP, claiming it was not conducted properly, rather than to learn that millions were spent conducting it due to prior reports of cloud seeding increases in snow that were illusory.

 I showed a graduate student friend, Tom Matejka, that first reviewer’s reject letter.  Tom, laughing, drew the following cartoon of how he thought that reviewer saw me:

 I still treasure this political cartoon by Tom.

But, unknown to me at this same time, CSU cloud seeding researchers were on the brink of retracting their results for the more prestigious Climax experiments.

My five-season experience as a forecaster, and having worked under orographic precipitation specialist, J. Owen Rhea, during the CRBPP gave me the knowledge and wherewithal to do it.  It may sound “crackpotty”, but I felt I had a responsibility to do it since no one else was going to and I “knew the territory.”  I couldn’t just walk away from it.  All that was learned during the CRBPP strongly suggested there could not have been snow increases due to seeding in the prior CSU experiments.


It took me about another week to look at the other reviews contained in that manila envelope Silverman had sent as I pondered the size and effort I had put into what surely was going to be Anand content in  enormous failure.  I am sobbing right now remembering that time; tears flowing!9 Where did this come from?  I haven’t thought about this chapter of my life in decades, but it’s like the same exact feelings I had so long ago have body-slammed me as I write about them!  Maybe I need a grief counselor…

When I finally had the courage to look at the other reviewers’ assessments, they both recommended, “accept” with revisions.

I wept uncontrollably again.  I was going to “get in” after all, though it would now be without Prof. Hobbs purview in carrying out “revisions” required by the reviewers.   Why did Prof. Hobbs wash his hands of my effort at this point?  Answer:  over the placement and content in an acknowledgement.


Professor Hobbs washes his hands of the WCPE manuscript before the final submission

By the time that the reviews had come in, Prof. Peter Hobbs had washed his hands of my manuscript.  Prof. Hobbs had written an acknowledgement for himself and had placed it ahead of that for J. Owen Rhea whom I had originally placed first.  Owen Rhea was the initial lead forecaster for the CRBPP, and later, Acting Project Manager under whom I worked.  I had learned so much working for him concerning orographic precipitation patterns.  I don’t recall that I had thanked Prof. Hobbs in those early drafts after he improved them.  I only have a  1977 draft, prior to Peter’s scrutiny in which this acknowledgment appeared in which I REALLY wanted to thank the CSU’s Prof. Grant and his staff:

“Acknowledgements. The author would like to thank Paul Willis of the National Hurricane Research Laboratory and Dr. J. Owen Rhea of Colorado State University who, as Project Manager and Project Forecaster, re­ spectively, for the first season of the Pilot Project, provided many insightful and illuminating discussions of the Colorado State University cloud seeding experiments which helped inspire this paper. I would also like to thank Professor Lewis O. Grant and the staff of Colorado State University for their unhesitating cooperation and willingness to examine “both sides of the coin.” Appreciation is also given to Mr. Larry Hjermstad of Western Weather Consultants in Durango for his cooperation in providing climatological data and copy facilities at a low cost, and Mr. Travers T. Ward for copying it all.”

The 1979 acknowledgement in the WCPE reanalysis publication was this:

“Acknowledgments. The author wishes to extend his deepest appreciation to Dr. J. Owen Rhea for his in­ valuable encouragement, comments and criticism during the course of this research. Particular thanks is also due Professor Peter V. Hobbs whose cogent editing and restructuring of this paper greatly improved its presentation and coherence. A review by Dr. Colleen A. Leary also improved the intelligibility of this paper. I would also like to thank Professor Lewis 0. Grant and the staff of Colorado State University for their unhesitating cooperation and willingness to supply data and, other information relative to the WCPE.  Appreciation is also extended to the Bureau of Reclamation, Division of Atmospheric Water Re­ sources Development, and to Mr. Larry Hjermstad for supplying data relative to the Colorado River Basin Pilot Project. The author is also indebted to Mr. Travis T. Ward of Durango for his copying of the numerous copies of Climatological Data requested by the author.”

Peter Hobbs also suggested at one point that he would normally be a co-author after editing and improving the presentation of manuscripts like mine.  I didn’t take the hint; maybe I should have?

I journeyed on and the revised version of the manuscript went to the journal in the fall of 1978 without Peter Hobbs’ expert purview.  I had now alienated perhaps my only ally, certainly the most important one.

Speculation on the fallout from the acknowledgement kerfuffle with Prof. Hobbs

The above happenstance may also explain why Prof. Hobbs took first authorship on the reanalysis I did of the Skagit Project (Hobbs and Rangno 1978) done on my own initiative, but while at work in Prof. Hobbs’ group.  It was submitted to the journal after the WCPE manuscript was submitted but was accepted and published ahead of it. I then I became concerned that it might appear that Prof. Hobbs had directed me, a little-known player in the weather mod game, in the WCPE paper that was to follow.  It would make sense that a grand player in the weather mod arena like Prof. Hobbs had directed an under credentialed subordinate on how to reanalyze cloud seeding experiments.

An inappropriate authorship sequence was the case, too, in the work I did that undermined the foundations of the Climax and Wolf Creek Pass experiment that was published as, “Hobbs and Rangno” 1979, J. Appl. Meteor.  Prof. Hobbs even presented this work as a sole authored work at the International Conference on Cloud Physics at Clermont-Ferrand.   I acceded to these authorship acts, though they were unsettling.   Only recently did I blow a gasket when I discovered this caption under Figure 2 of Hobbs (1980):

Issues of credit and authorship within Prof. Hobbs’ group have persisted right up until today (2021), when a senior faculty member, formerly in Prof. Hobbs’ group, could not cite a paper on rainbands where Prof. Hobbs was the lead or sole author because he had not done the work and knew who did.  I know that a reader at this point would say, “Get over it!”  Sorry, can’t.


ALR, with a life story vignette by someone who only wanted to forecast weather when he came to Durango. Thanks for reading it, if you do.


1An example of a pen and ink spreadsheet I did in the late 1970s for those younger researchers who can’t imagine such a thing. You can’t imagine how many of these kinds spreadsheets I did in support of the WCPE reanalysis!  Dozens at least. Bottles of Shaefer’s ink were consumed!

2I remembered, Ann Stone, and that third grade math humiliation where Ann was to add up a column of five of the same number, and I was to multiply that number by five, all this with both of us at the blackboard in front of the class.  I was to demonstrate how much faster multiplying something was than adding up a column of the same number.   I couldn’t do that multiplication while Ann finished quickly.

6J. O. Rhea, Prof. Grant’s grad student, personal communication,  1975.

3The Bureau of Reclamation specified that the seeding contractor, E. G. & G., Inc., personnel draw their own regional surface, 700 and 500 hPa weather maps rather than rely on National Weather Service facsimile maps. I was a good weather map drawer/artist.   Since it’s fall, I will use this map with a bit of humor in it.

4Recently, having a different perspective, I have deemed this Durango Herald article as a tongue-in-cheek, “Historic Moments in Weather History:  “Art Rangno EXPLODES onto the weather mod scene”, a title meant to generate a smile.    I was to work on reanalyses and critical commentaries on cloud seeding experiments for the next 45 years!  Still am!  What is the matter with me?  Get a life!  Haha, sort of.

5That was to happened later….several years later, and had to do with asking for an investigation of some possible real science crime; withholding results that might have prevented the multimillion dollar CRBPP randomized cloud seeding experiment from taking place.

7I was going to take the place of their, “Flight Meteorologist,” Don Atkinson, who later confided in me that he thought the job I was going to take, his, was a “dead end.”   Atkinson was resigning to go get his master’s degree in business administration. He eventually returned as the business administrator for the University of Washington’s Atmos. Sci. Department.

8Rhea presented for Grant et al. who was officially listed as the presenter.

9That surprise grief attack happened a few months ago when I first started rehashing this “life chapter” after forgetting about for so many decades.   I seem more inured to emotions about this as I go through  draft today.





I was so excited…

 My trip, and the analysis of the data that came out of it,  was the first published report that something was not right with Prof. Gagin’s cloud reports.  My publication appeared in the Quart. J. Roy. Meteor. Soc., Rangno 1988, “Rain from Clouds with Tops Warmer than -10°C in Israel,” hereafter, “R88,” found here).  My manuscript was “communicated” to the Quart. J. Roy. Meteor. Soc. by the director of our airborne research group,  Prof. Peter V. Hobbs, a member of the Royal Society eligible to submit papers to that journal.  (I was not).

Neither Prof. Hobbs nor I believed that my paper refuting the many published descriptions of Israeli clouds by Prof. Gagin could be published in an American Meteorological Society journal.  Too many potential reviewers had heard Prof. Gagin’s presentations on too many occasions, or read his journal papers,  to believe that what he was saying could be so much in error.

R88 was based on rawinsonde-indicated cloud tops when it was raining at the launch site or within an hour and a half, so it was fairly primitive.  Why I had only rawinsonde data and not data from Prof. Gagin’s 5-cm modern radar data as was explained in Chapter 4.

Nevertheless, my “primitive” findings were confirmed several years later in independent airborne studies (e.g., Levin 1992, 1994, preprints; Levin et al. 1996, J. Appl. Meteor.) and on several occasions since then (e.g., Freud et al. 2015).  Spiking football now!

Why Prof. Gagin’s cloud reports were likely in error and how much they deviated from comparable clouds was shown in Rangno and Hobbs 1988, Atmos. Res.

I had experienced cloud seeding “delusionaries” in Colorado during the CRBPP, namely, credentialed “scientists” who believed things that weren’t true and even published things they knew weren’t true (as Grant and Elliott had done in 1974, J. Appl. Meteor.).  I sensed that Prof. Gagin might be one of those.  He and his staff also had a lot to lose if the clouds of Israel weren’t so ripe for seeding as his descriptions painted them.

I reprised my 1988 published findings from my trip to Israel in a University of Washington Atmos. Sci. colloquium in February 1990. I was motivated by the J. Appl. Meteor. memorial issue to Prof. Gagin in October 1989.  Here’s the flyer for that talk, intended to draw interest with some topical humor concerning the Iran-Contra affair that was in progress while I was in Israel in 1986 (unknown to me at the time):

End of life story.  I consider this episode concerning Israeli clouds my greatest, costliest, volunteer science contribution of the several reanalyses that I did on my own time and dime.




The trip to Israel

My self-funded trip to Israel was one of 11 weeks, from January 4th  through March 11th, 1986.  I loved my time in Israel and would go back in a heartbeat any winter to see those beautiful Cumulus and Cumulonimbus clouds rolling in off the Mediterranean again!

Following my return and for the rest of 1986 I lived off my savings in Seattle to write up an analysis and draft of what I had found.  Despite my resignation, Prof. Hobbs and I retained a civil relationship as I also finished grant work that I said would before resigning (which ended up being Rangno and Hobbs 1988, Atmos. Res., “Criteria for the Onset of Significant Ice Concentrations in Cumulus Clouds.” In this short 1988 paper, it was noted that the reports from Israel concerning the onset of ice in clouds was sharply at odds with similar clouds.  I discussed why that might have been in the paper.

Prof. Hobbs also agreed to look over my drafts and figures of the Israeli cloud investigation as I brought them in to the University of Washington from time to time.  Being who he was, Prof. Hobbs greeted me when I first dropped by the University of Washington upon my return from Israel with, “I doubt you’ll get a paper out of your trip.”  However, I knew exactly what I had to do to pass journal muster because of the rejection of that 1983 paper.  It was also evident that no American Meteorological Society journal was likely to accept a paper like the one I was putting together;  too many potential reviewers had heard at conference or read in journal articles on too many occasions how Prof. Gagin had described Israel’s hard to rain natural clouds.

That I got any Israeli data at all to take home and analyze was to the credit and magnanimous view of my outside cloud inquiry by the Israel Meteorological Service (IMS), Director, Y. L. Tokatly, who gave me pretty much a free reign to examine historical balloon soundings and synoptic maps within their Climate Division.  The Climate Division was headed by Sara Rubin, who was also friendly and extremely helpful.  I was even given a little desk space in the climate division!  I went there every day that there wasn’t a storm to experience, clouds to assess with this experienced eyeball and photograph while traveling all over central and northern Israel on their stupendous bus system.  I had also crated my bicycle to Israel for local travel.

Here is the IMS Headquarters building I worked in and the little desk space they gave me, two of the several officemates I had, and a shot of the IMS map and briefing room.

Zohar Moar (?) working next to my little desk space in the Climate Division office of the IMS.

Ronit Ben-Sara and Geulah Siles in the climate division office.

Forecaster Uri Batz in the IMS map room.

Below these is a list of the bus rides I took on ONE storm day, always sitting behind the driver and looking out the front window, recording drop sizes and nature of the rain  on  the  front  window::

In some interesting cases, such as in the hill region and the Golan Heights, I would get out and walk around in the wind and clouds, the latter often topping a hill region such as Jerusalem.   I had my heaviest clothing, but it really wasn’t enough to keep me warm, and I had no gloves. Temperatures during storms were usually in the low 40s in Jerusalem with winds of 20-30 mph and passing showers.  Once, I could not pull the shutter lever on my Rolliecord film camera to take a cloud photo my fingers were so cold.

This weather, too, really put an edge on those Bible stories.  I could not imagine how miserable it really was for people living here in the winters.  It even snows in Jerusalem from time to time as I saw myself in a January 1986 storm pocked with thunder.   I listened to the IMS weather briefings most mornings, too.  I was in heaven.

First Impressions

What was particularly interesting to me was that I encountered more skepticism about Israeli cloud seeding efforts in the IMS than there seemed to be in the entire world outside of it!

My first meeting with Prof. Gagin:   January 10, 1986

It was an extremely cordial meeting in his office at the Rivat Gam branch of the Hebrew University of Jerusalem at the end of a dry week in Israel.  That was followed by a family dinner at his residence where he regaled me with so many interesting stories.  I really thought at that time that he didn’t mind my intrusion into his cloud seeding world, and I began to feel some guilt about it since he was so nice to me!  But I had to persevere in my “task” I thought.

Prof. Gagin took this photo atop the HUJ satellite campus at Rivat Gam during that first meeting. He would not allow me to take his photo.  I also suggested at this time that if I “found something” that perhaps we could co-author a paper.  He deferred.

Not too surprisingly, all the weather forecasters I spoke with in the Israel Meteorological Service in 1986 were well aware that clouds much shallower than Prof. Gagin was describing as seeding targets, that is, those with tops >-10°C rained.  It must have seemed bizarre to them that I had come 7,000 miles to document something they deemed so ordinary!

But where were Tel Aviv University atmospheric scientists in in these matters?  Think how embarrassing it might be to all Israeli scientists to think that a minor foreign science worker had  traveled thousands of miles to inform them about the true nature of their own clouds as they were described in the peer-reviewed literature!

You may have guessed the possible answer to this puzzle about the lack of involvement of other scientists in questioning or overturning Prof. Gagin’s cloud reports.

It turned out that considerable funding from cloud seeding operatives in Israel went to Tel Aviv University (Z. Levin, 1986, private conversation).  He simply could not openly help me, he stated, in our one and only meeting.   He also had trouble believing at that time that my cloud assessment (ice particles onset in Israeli clouds with tops between -5°C and -8°C, and that concentrations of “50-200” per liter were present by the time cloud tops reached -12°C, was correct.  I wrote this same assessment following my 2nd meeting with Prof. Gagin to Professors Roscoe R. Braham, Jr., at North Carolina State University, Gabor Vali, University of Wyoming, Peter V. Hobbs and  Lawrence F. Radke at the University of Washington, and to Dr. S. C. Mossop (of the Hallett-Mossop riming and splintering process).  Why I wrote to them will become clear in the next segment.

January 19, 1986:  My second meeting  with Prof. Gagin

There had been several shower days in Israel when Prof. Gagin and I met for the second time.  He asked me at the very beginning, after handing me a cup of coffee,  “What have you found?”

I unloaded a boatload of findings contrary to his cloud reports.  Suffice it to say, our meeting did not go well after that.  In a sense, I was Professor Gagin’s nightmare; an under-credentialed worker coming to “his house” to expose faulty cloud reports.  But, with his radars and aircraft, how could he possibly not have known that his reports were faulty?

I had also felt true drizzle falling in Jerusalem in the early morning hours during the very first storm.  Drizzle tiny (<500 um in diameter) drops that are close together was something that was not supposed to occur in Israel due to the polluted nature of the clouds reported by Prof. Gagin.   I certainly did not expect to see it, and when I stuck my hand out of my apartment window, I yelled, “drizzle?” to no one in particular.

Then, when I came down from Jerusalem on a bus that morning to the coastal plain, I was amazed by shallow, glaciating clouds (modest Cumulonimbus clouds) rolling in from the Mediterranean Sea.  Namely, in less than three hours of the first storm, I had seen all I needed to know that Prof. Gagin’s clouds reports had described non-existent clouds.

In this 2nd meeting, I had brought with me an IMS sounding from Bet Dagan when rain was falling lightly throughout the hill region of Israel that had a cloud top, marked by a sharp inversion and strong drying,  at -5°C.  Professor Gagin was non-plussed by the sounding, stating that balloon soundings are unreliable for the purpose of assessing cloud top temperatures.

Prof. Gagin Had Heard Enough.

He informed me how offended he was by my visit to check his cloud reports.  He asked me, “Who do you think you are, the Messiah, come to expose the liars?” He immediately then asked, “Did Hobbs send you?”

Peter Hobbs had not sent me5! !

I was reeling at that point in my meeting with Prof. Gagin, almost speechless even though I knew something like this, being bawled out,  might happen.   However, I did cough up an admonition: “Don’t be like Lew Grant,” referring to Grant’s stubbornness in accepting new information.  Prof. Gagin replied, “I don’t appreciate the comparison.”  This is the first time I have mentioned this quote.  Prof. Grant deemed Abe Gagin a good friend and wrote a testimonial on his behalf when Prof. Gagin died.  I would be willing to bet that Prof. Gagin later deeply regretted uttering that about Grant.

Before many more words were spoken, Prof. Gagin was escorting me out of his office and telling me not to come back; “Do your own thing,” he said.  I went back to my apartment and wandered down King David boulevard in Jerusalem in kind of a haze.

For me, to “do your own thing” was continuing to gather historical data at the IMS on fair weather days and travel around eye-balling and photographing clouds and rain on storm days.  I decided I needed to alert my former colleagues at the University of Washington and other scientists in this field about what had happened and what my so-called, “findings” were.  I wrote to five leading scientists of the day, Prof. Peter V. Hobbs and Prof. Larry Radke at the University of Washington, the leaders of my former group, to Professor Roscoe R. Braham, Jr., at North Carolina State University, Professor Gabor Vali, at the University of Wyoming, and to Dr. S. C. Mossop at the Commonwealth Science and Industrial Organization in Australia.  All wrote back except Hobbs and Radke who were on a field project in North Carolina.

All that replied supported what I was doing.  Vali described my investigation as “spectacular,” and Mossop stated that I was a “genius for discovering sometimes unwelcome results.”  Mossop was alluding also to my discovery of that an aircraft can create ice in clouds at temperatures around -10°C (Rangno and Hobbs 1983, J. Appl. Meteor.) a paper that had little credibility until confirmed in trials eight and 18 years later, it was that unexpected.

I  felt an obligation to tell ASAP what had happened with Prof. Gagin to IMS Director, Y. L. Tokatly, in case he might wish to revoke my visitor privileges.  He did not!  He replied that it was just a difference of opinion, and I could continue to visit the IMS and gather data!  How magnanimous was that?

February 3rd, 1986:  My Third and Last Meeting with Prof. Gagin Takes Place at His Ben Gurion AP Radar.

A third meeting was arranged, despite what had happened in our 2nd meeting, after I learned that Prof. Gagin and his cloud seeding group had their own radar located on the outskirts of Ben Gurion AP.   I did not even know that Prof. Gagin had his own radar at that point until informed of the “private radar” by an Israeli air traffic control person when I was looking for pilot reports of cloud tops!  I had to call Prof. Gagin, as hard as that would be, and ask him about visiting it.  A third meeting was arranged.  Prof. Gagin was cooperative.

But what about that radar, located on the outskirts of Ben Gurion Airport?  That radar would surely prove that Prof. Gagin was right and I was wrong; that rawin soundings indicating high cloud top temperatures of precipitating clouds were, indeed, unreliable as Prof. Gagin asserted.

I bicycled from my Riviera Hotel in Tel Aviv to this meeting.  The sky was overcast in deep Altostratus (a mostly ice cloud) underlain by Altocumulus opacus clouds.  A storm was approaching, but it would be hours before rain arrived.  Below, a vertical look at those clouds from the site of the Ben Gurion radar as I was leaving.

The main thing I wanted to ask Prof. Gagin in our third meeting was whether I could go to this radar during storms and see cloud top heights.   He said “no,” giving “airport security” as the reason.  He repeated to me  how (understandably) offended he was by my visit to Israel to check his cloud reports.

But, “airport security?” I had just bicycled to his radar on the outskirts of Ben Gurion; no problem!  Later, a grad student at Tel Aviv U. in Professor Zev Levin’s group,  Graham Feingold, would erupt over the “airport security”  claim as a lie, as it clearly seemed to to be at the time.

Prof. Gagin further assured me in this meeting at his radar that radar top measurements would only confirm his reports (that is, if I could only view those top heights on his radar!)

I also informed Prof. Gagin that due to his behavior in our 2nd meeting that I had asked several scientists around the world to intervene with him on my behalf.  He asked me who I had written to and I told him (those listed earlier).

How crazy was this episode?  

A minor, but well-known cloud seeding critic, as I was at that time, could be easily convinced that he was wrong by examining Prof. Gagin’s  radar top height measurements.  But he was denied the opportunity to be proved wrong!

Learning about private flying in Israel and then getting a pilot to be on “standby” for cloud sampling

Late in February,  I learned that there was a robust private aircraft touring business in Israel.  I had assumed, based on the reports of Professors Mason, Hobbs, and Vali,  that research groups weren’t able to get in, that flying around in Israel to sample clouds couldn’t be done due to security issues.  But then, how could there be a strong tourist flying program?

I then went to one of the aircraft touring sites at Sade Dov Airport near Tel Aviv, and found that I could get a single engine aircraft and pilot, Yoash Kushnir, who would sample the tippy tops of clouds along the coastline of Israel with me along.  He said it would cost $250 an hour and I was willing to spend about $500 to do give it a try.   His aircraft had a ceiling of about 14 kft as I recall,  just “high enough” to sample cloud tops that would average >-10°C.  Tippy tops is not the best place to find much ice.  Higher concentrations of ice are found lower down when ice is developing, as a rule, unless the top has completely glaciated.

The pilot I had on standby, incidentally, was angry that it was believed outside of Israel that you couldn’t fly research in Israel and sample clouds.  It was a presumption I had, too, because the University of Wyoming and the British teams were not able to get in to sample Israeli clouds.  This pilot regularly flew tourists to view ruins at Masada and other historical sites in Israel.

While Prof. Levin felt he could not openly support my efforts due to funding issues, he did provide me with a graduate student, Graham Feingold, who was willing to go along on a flight.  He  would act as a witness to what was found in those “tippy tops.”  I had planned to use the “black glove” technique used decades earlier in sampling clouds for the presence of ice.  You literally stick a black-gloved hand (or a black stick) out of the window of the aircraft and look for what hits.

You can only imagine how crazy these people thought I was!  Years later I learned that I had been described by Graham, who was to become my friend, as, “that cowboy from America.”

No flight ever took place as the weather dried out by the time l learned I could hire an aircraft to sample cloud tops.  Ironically, the only rain after having Yoash Kushnir on standby fell briefly from clouds whose tops were near the freezing level, and likely, if I had flown that morning, no ice would have been found in them!  It was a surprise weather event that produced barely measurable rain.

My Meeting with Israeli experiments’ “Chief Meteorologist,” Mr. Karl Rosner

Late in my 1986 cloud investigation, I met the Israeli cloud seeding experiments’ “Chief Meteorologist,” Mr. Karl Rosner.  It was IMS’ scientist, Alexander Manes, that got me in touch with him.  I learned that the chief meteorologist, too, knew that Israel clouds rained having tops warmer than -10°C!  It then seemed that the only three people in Israel who did not know that rain fell from such clouds were those who studied them in great detail, Prof. Abe Gagin, his frequent co-author, Jehuda Neumann,  and Prof. Gagin’s only graduate student, Daniel Rosenfeld!

But Mr. Rosner had a more important and astounding thing to tell me:  Prof. Gagin had refused to publish the result of the south target random seeding for Israel-2.   Mr. Rosner had launched a campaign to see that it got published.  The results of the “full” Israel-2 experiment were published by Gabriel and Rosenfeld (1990).   Prof. Gagin, his co-author, J. Neumann, had stated in their 1981 journal paper that the seeding of the south target was “non-experimental.” They wrote that this was due to the lack of a suitable coastal control zone like the that they used to evaluate the north target’s random seeding.  Previously, in 1974 these authors had given the result of random seeding in the south target as suggesting a decrease in rain after two rain seasons, and by 1976 at conference, stated the south target results were inconclusive for the full Israel-2 experiment.

So, here I was questioning the cloud reports and then learning from Mr. Rosner that half of the Israel-2 experiment had not been reported!  In Gabriel and Rosenfeld’s 1990, we learned that the “full” result of Israel-2 was a -2% suggested effect on rainfall;  it had not replicated Israel-1 as was previously believed based on the partial reporting of Israel-2.

Some Speculation About Why Prof. Gagin Might  Not Known Have Known About the Natural Precipitating Nature of Israeli Clouds

It may be that Prof. Gagin’s graduate student knew the true cloud/rain situation but did not pass that crucial information along.  It does happen that lab directors and important scientists have staff and students who do all the research, and upper echelon scientists are not close to what’s being done by the lower echelon staff;  the latter might not pass along all the relevant information if it goes against the beliefs of their bosses.

One must conjure up a dizzying amount of incompetence concerning the three principal Israeli cloud seeding researchers (Gagin, Neumann,  and Rosenfeld) who could not identify the most basic aspects of their clouds;  the depth  and cloud top temperatures  at which they started to rain.

But is an “incompetence” hypothesis credible? Or was it that a knowing graduate student did not pass along to Prof. Gagin information that would have eroded his cloud reports?  Read on….

Prof. Gagin and his student had monitored cloud tops with a vertically-pointed radar with tops having been confirmed by aircraft flyovers.  This was done for two rain seasons in the late 1970s (Gagin 1980, Atmos. Res.)  Prof. Gagin made no mention in his article of the shallow raining clouds that violated his cloud reports, ones that had to have passed over his radar during those two rain seasons.

Dr. Rosenfeld studied radar data and satellite cloud patterns in his 1980 master’s thesis and 1982 Ph. D. dissertation2.  Yet, he did not bring to his country’s attention or to the scientific community, those shallow raining clouds with relatively warm tops, either.  Such reports, if outed, would have had a profound effect on the viability of cloud seeding to increase rain in Israel, perhaps saving the country 10s of millions of dollars in wasted seeding efforts, as we now know happened when an independent panel (Kessler et al. 2006) found no via evidence that cloud seeding for 27 rain seasons had increased runoff into Lake Kinneret (Sea of Galilee).

Moreover, these researchers were recording echo top data from their Enterprise 5-cm wavelength radar at Ben Gurion AP after it had been deployed in support of cloud seeding efforts in the late 1970s.  Dr. Rosenfeld cited 1986 recorded radar top data in his 1997 “Comment” on the Rangno and Hobbs 1995 J. Appl. Meteor. paper.  Another enigma.

 A regret about stridency

My last communication to Prof. Gagin following my cloud investigation trip was from Seattle in June 1986.  In that long letter I recapitulated the elements of my cloud investigation.  This letter was copied to Prof. Peter Hobbs, Roscoe R. Braham, Jr.3, at North Carolina State University, and Prof. Gabor Vali at the University of Wyoming.

The one thing I came to regret was how I closed that June 1986 letter.  I closed it with a challenge:  That I, myself, would leave the field of meteorology, all aspects, if my Israeli cloud observations were wrong; that ice was not forming in high concentrations in Israeli clouds with top temperatures >-12°C (eyeballing 50-200 per liter as I wrote in my letters from my experience sampling glaciating clouds at the University of Washington).   I then challenged Professor Gagin himself to leave the field of meteorology instead of me if my observations were later proved correct:

So, there I was, the person who was told to give up meteorology by Joanne Simpson, who believed that “statues will be raised in his honor” challenging that very professor to quit the field.

Joanne likely never remembered who I was, and I had a couple of cordial correspondences with her due to my cloud seeding reanalysis publications that began reaching the literature in the late 1970s and early 1980s.  Later, when it was thought there was  some overarching claims about “global warming,” she sent me her banquet talk given in October 1989 to a statistical conference, shown here to indicate this cordial relationship:

1990 1-22 Simpson, from, about GW and cloud seeding_color version_ocr

I wish I had gotten to know her.

The End


Joanne Simpson’s homage to Prof. Gagin:


1This was, and is even today (!),  a sore point for me; that someone might believe this.  Prof. Hobbs was clueless about Israeli cloud anomalies and the Israeli experiments except for those plots and information that I relayed to him while studying those experiments on my own time.  As most professors would do,  he read in the peer-reviewed literature and took it at face value.

2Rosenfeld’s works are in Hebrew and have never been translated into English, but should be.

3The full letter, and others that I wrote to Prof. Roscoe R. Braham, Jr., are in an archive of his professional correspondence at North Carolina State University.


By the end of the 1970s, Prof. Gagin and his work had become of interest to me.  After all, as I learned in Durango, nothing could be taken at face value in the cloud seeding literature unless I had personally validated that literature by scrutinizing every detail of the published claims in it, looking for omissions and exaggerated claims, something reviewers of manuscripts certainly did NOT do.

I had a lot of experience by this time.  I had reanalyzed the previous published reports of cloud seeding successes in the Wolf Creek Pass experiment (Rangno 1979, J. Appl. Meteor.);  the Skagit Project (Hobbs and Rangno 19781, J. Appl. Meteor.), and had authored comments critical of the published foundations of the Climax and Wolf Creek Pass experiments in Colorado (Hobbs and Rangno1 1979, J. Appl. Meteor.) and others.

What was to transpire was that the person Joanne Malkus Simpson suggested to give up meteorology, me, helped eliminate the reasons why anyone, let alone her, would continue to believe that “statues” should be raised to honor Prof. A. Gagin’s contributions to cloud seeding.  Here’s what happened.

The Israel chapter of my cloud seeding life begins

In about 1979, the Director of my group at the University of Washington, Prof. Peter V. Hobbs, challenged me to look into the Israeli cloud seeding experiments:  “if you really want to have an impact, you should look into the Israeli experiments.”  I guess he thought I had a knack seeing through mirages of cloud seeding successes.

I did begin to look at them at that time.  Prof. Hobbs asked me to prepare a list of the questions I had come up with after I started reading the literature about the Israeli experiments.  He wanted to ask questions of Prof. Gagin at the latter’s talk at the 1980 Clermont-Ferrand International Weather Modification conference in France.  Those at the conference said that he did ask Prof. Gagin questions but it wouldn’t have been like Prof. Hobbs, as I began to learn over the years in his group, to have said, “My staff member has some questions for you, Abe.”  Maybe he thought that wasn’t important.

I already knew something of the rain climate of Israel long before reading about the Israeli cloud seeding experiments.  This was due to a climate paper I was working on when I arrived in Durango, CO, as a potential master’s thesis for SJS.  My study was about “decadal” rainfall shifts in central and southern California and I wanted to know if what I observed in California had also been observed in Israel, a country with long term, high quality rainfall records and one having a Mediterranean climate like California.  I received several publications from the Foreign Data Collections group at the National Climatic Center in those days, such as Dove Rosnan’s 1955 publication, “100 years of Rainfall at Jerusalem.”

So, I was not coming into the Israel cloud seeding literature “blind” to its surprisingly copious winter rain climate.  Jerusalem averages about 24 inches of rain between October and May, something akin to San Francisco despite being much farther south than SFO.

My interest in the Israeli cloud seeding experiments, however, ebbed and flowed in a hobby fashion until the summer of 1983 when I decided to plot some balloon soundings when rain was falling, or had fallen within the hour, at Bet Dagan, Israel, and Beirut, Lebanon, balloon launch sites. Anyone could have done this.

The plots were stunning!

Dashed line is the pseudoadiabatic lapse rate; solid line, the adiabatic lapse rate.   The synoptic station data are those at the launch time or within 90 min.  

Rain was clearly falling from clouds with much warmer tops at both sites than was being indicated in the descriptions of the clouds necessary for rain formation in Israel  by Prof. Gagin, descriptions that made them look plump with seeding potential.  His descriptions were of clouds having to be much deeper, 1-2 km,  before they formed rain.   And those descriptions were key in supporting statistical cloud seeding results that gave the first two experiments, referred to as Israel-1 and Israel-2,  so much credibility in the scientific community (Kerr 19821, Science magazine).    The deeper clouds described meant that there was a load of water in the upper parts of the clouds that wasn’t coming out as rain.  

Shallower clouds that were raining meant that there wasn’t going to be so much water in deeper clouds that could be tapped by cloud seeding; much of it would have fallen out as rain before they reached the heights thought to be needed for cloud seeding.

I also scrutinized Prof. Gagin’s airborne Cumulus cloud reports that appeared in the early and mid-1970s.  I found several anomalies in them when compared to other Cumulus cloud studies and our own measurements of Cumulus clouds.  One example:

While the 3rd quartile droplets became larger above cloud base as expected, droplets >24 um diameter were nil until suddenly increasing above the riming-splintering temperature zone of -3° to -8°C.  Those larger drops should have increased in a nearly linearly way as did the 3rd quartile drop diameters. If appreciable concentrations of  >24 um diameter droplets had been reported in this temperature zone, cloud experts would have deemed them ripe for an explosion of natural ice, not for cloud seeding.  So this odd graph left questions.

Too, the temperature at which ice first appeared in Israeli clouds, according to Prof. Gagin’s reports, was much lower than similar clouds as seen by data point 8 in the figure below constructed in 1984 (published  in  1988,  Rangno  and  Hobbs,  Atmos.  Res.)

When I read about how seeding was carried out in the first experiment, Israel-1,  I learned to my astonishment that only about 70 h of seeding was done during whole winter seasons upwind of each of the two targets by a single aircraft.  I concluded that there could not possibly have been a statistically significant effect on rainfall from seeding clouds given the true precipitating nature of Israeli clouds, the number of days with showers,  and the small amount of seeding carried out.  In Israel-2, the experimenters added a second aircraft and 42 ground cloud seeding generators (NAS 1973).  They, too,  must have realized they hadn’t seeded enough in Israel-1, I though.

Another red flag jumped out in the first peer-reviewed paper that evaluated Israel-1 by Wurtele (1971, J. Appl. Meteor.),   She found that the greatest statistical significance in Israel-1 was not in either one of the “cross-over” targets, but in the Buffer Zone (BZ) between them that the seeding aircraft was told to avoid.  This BZ anomaly had occurred on days when southernmost target was being seeded.   In her paper, Wurtele quoted the chief meteorologist of Israel-1, Mr. Karl Rosner, who stated that the high statistical significance in the BZ could hardly have been produced by inadvertent cloud seeding by the single aircraft that flew seeding missions.

The original experimenters, Gagin and Neumann (1974) addressed this statistical anomaly in the BZ  but did attribute it to cloud seeding based on their own wind analysis.

A Hasty 1983 Submission

Armed with all these findings, I decided to see how fast I could write up my findings and submit them to the J. Appl. Meteor.;  I came into the University of Washington on July 4th, 1983, and wrote the entire manuscript that day. I submitted it to the J. Appl. Meteor. the next day.    (Prof. Hobbs was on sabbatical in Europe at this time.)

I was sure it would be accepted, though likely with revisions required.  No reviewer could not see, I thought, that there was a problem with the existing published cloud reports from Israel.

My conclusions were against everything that had been written about those experiments at that time, that the clouds were not ripe for cloud seeding, but the opposite of “ripe” for that purpose.

In retrospect, it wasn’t surprising that I was informed six months later that my manuscript was rejected by three of four reviewers: “Too much contrary evidence.  You can’t be right” was the general tone of the message.

Nevertheless, I was surprised by the rejection, thinking my evidence was too strong for an outright rejection.  I tried to make the best of it in a humorous way to the journal editor, Dr.  Bernard A. Silverman, passed the news along.  I hope you, the reader, if any,  smile when you read this: In 1984 at the Park City, UT, Weather Modification Conference, I had my first personal interaction with Prof. Gagin.   I was giving an invited talk with an assigned title at that conference about the wintertime clouds of the Rockies, “How Good Are Our Conceptual Models of Orographic Cloud Seeding?”

Prof. Gagin  informed me that he had been one of the four reviewers of my 1983 rejected manuscript.  He “lectured” me sternly between conference presentations about how wrong I was about his published descriptions of Israeli clouds that had a hard time raining naturally until they got deep and cold at the top.

Rejection and Lecture Have No Effect

The rejection of my 1983 paper and Prof. Gagin’s “lecture” about how wrong I was about Israeli clouds, however, had no effect whatsoever on what I thought about them. 

I felt I could interpret balloon soundings just fine after the hundreds and hundreds I examined in Durango with the CRBPP while looking out the window to see what those soundings were depicting.  I marveled, instead, that reviewers couldn’t detect the obvious, especially Dr. Bernard A. Silverman, the Editor of the J. Appl. Meteor.

After that rejection that moved on to studies of secondary ice formation in clouds in Peter Hobbs group, published in Hobbs and Rangno 1985, J. Atmos. Sci.), but the thought of going to Israel began to surface.    Someone has to do something!

It was about this time that I read about American physicist, R. W. Wood, going to France to expose what he believed to be the delusion of N-Ray radiation reported by Prosper René Blondlot (Broad and Wade 1982, Betrayers of the Truth).  I thought, “I bet I could do that same kind of thing,” thinking that  Prof. Gagin might well be similarly deluded about his clouds.  

A Resignation Followed by the Cloud Investigation Trip to Israel 

And so, following the historical precedent that R. W. Wood set, I hopped on a plane to Israel at the beginning of January 1986 following my resignation from Prof. Hobbs’ Cloud and Aerosol Research Group.

Resigning from the Job I Loved .

My resignation was in protest over issues of credit here and there that had been building up for nearly a decade in Peter Hobbs group2.  Peter had lost several good researchers over this same issue.  In a late December 1985 meeting with Prof. Hobbs prior to my January 1986 trip,  he described me as “arrogant” for thinking I knew more about the clouds of Israel than those who studied them “in their own backyard.”

“Confident” would have been more appropriate than the word, “arrogant” Prof. Hobbs had used.  I smirked when he said that; I couldn’t help myself.  I had done my homework in the process of writing that short paper in 1983 critical of those cloud reports when Peter was on sabbatical.  In fact, I was so confident about my assessment of Israeli clouds that I told Prof.  Peter Hobbs,  Prof. Robert G. Fleagle (also with the University of Washington) and Roscoe R. Braham, Jr.3,  North Carolina State University, and others, that I was about “80 % sure” of my assessment of Israeli clouds from 7,000 miles away even before I went.

My Agenda

It was true, however, that I wanted to show the world by going to Israel that I was the best at “outing” mistaken or fraudulent cloud and or cloud seeding reports, ones that were considered credible by the  entire scientific community, including Prof. Hobbs4.  However, virtually any low-level forecasting meteorologist could do what I did, especially storm chasing types like me, that was the fun of it.

And, here was a chance to do something that would be considered, “historic,” just like Wood’s trip to France was!

Another intriguing factor contributing to the idea of going to Israel was the statement expressed by Peter Hobbs to me a few years earlier; “No one’s been able to get a plane in there.”  He told me that British meteorologist and cloud physics expert, Sir B. J. Mason, had said the same thing to him.  I wasn’t a plane, but by god, I was going to “get in there.”   The view of Prof. Hobbs and Sir B. J. Mason  was later to be confirmed in a letter to me in Israel by Prof. Gabor Vali, University of Wyoming cloud researcher who wrote of six attempts to do airborne research of Israeli clouds, all denied.

Too, I looked forward to going to Israel and seeing what that country was like, too, with all of its biblical history.

And, if it was a case of delusion, as American physicist, R. W. Wood, encountered with the N-Ray episode, Prof. Gagin would be happy to cooperate with me and let me see radar tops of precipitating clouds. Prosper-René Blondlot had cooperated with Dr. Wood, allowing him to watch an N-Ray experiment.

But if Prof. Gagin didn’t cooperate with me, I could just hop on the next plane back to America.  I would “know” I was right about those clouds without even seeing them!


1Corrections to Kerr’s 1982 Science article were published by Prof. Hobbs in Science in October 1982.  In the original article, Prof. Hobbs inadvertently led Kerr to believe that he himself, and not me, had conducted the reanalysis and other work that undermined the Climax cloud seeding experiments.  Prof. Hobbs apologized to me as soon as he saw Kerr’s article. Still…..

2Authorship sequences on publications under Prof. Hobbs’ stewardship sometimes did not represent the progenitor of a work; i.e., that person who should be first author;  the person who originated the research, wrote the drafts describing results,  the person who had done all the analysis that went into it, as in these footnoted cases of authorship where  Prof. Hobbs had placed himself as lead author.    Prof. Hobbs was a wonderful science editor and made great improvements to drafts that he received.   The authorship sequence problem was to mostly go away after I resigned.

3My resignation letter was 27 single spaced pages!

4Prof. Braham kept the letters I wrote to him and they can be found in his archive at North Carolina State University.

5See Prof. Hobbs 1975 “Personal Viewpoint” comment in Sax et al. 1975, J. Appl. Meteor., “Where Are We Now and Where Should We Be Going?” weather modification review.


This story begins with my first full-time job after graduating from San Jose State College.  I was hired as a weather forecaster by E. G. & G., Inc.,  in Durango, Colorado in support of a massive randomized cloud seeding experiment called the Colorado River Basin Pilot Project (CRBPP).  It was intended to prove that seeding wintertime mountain storms was a viable way of adding water to western rivers over a large area.   I was to work under lead forecaster, J. Owen Rhea, an expert on wintertime mountain storm forecasting.  Paul Willis was the Project Manager.  The project was intended to replicate stunning cloud seeding successes reported in Colorado by Colorado State University (CSU) scientists, but in the CRBPP, over a much larger area than in the CSU experiments.

The Durango job was to change my life forever, and eventually lead me to Israel as a skeptic of reports of cloud seeding successes.  Ironically, that change was to involve North American Weather Consultants,  and it’s president, Mr. Robert D. Elliott, for whom I had worked in 1968 in Goleta, CA,  as a summer hire between semesters at San Jose State, and again when on loan from the CRBPP  in the summer of 1972 in statewide cloud seeding program in South Dakota.

By time the Colorado River Basin Project (CRBPP), the nation’s largest, most costly ever mountain randomized cloud seeding experiment  ended after five winter seasons,   I had become an orographic cloud seeding “apostate. ”

What caused this epiphany?

This metamorphosis from  an idealistic and naive forecaster  coming right out of college happened due to seeing what I think most scientists would term “misconduct” in the journal literature during the CRBPP in 1974 combined with misleading news releases from the BuRec sponsor of the CRBPP.  In the journal article,  the two authors were asserting things they knew weren’t true.  I personally knew that they knew this.  I decided that  I was going to do something about this deplorable situation after the CRBPP ended.

I then had come to believe that the cloud seeding successes reported by CSU researchers couldn’t possibly have been real ones  due to the many seeding impediments that turned up during the CRBPP (clouds not ripe for seeding as had been described, inversions that blocked the seeding material in the wintertime,  cloud tops not at the heights they were supposed to be, etc.)

It was very troubling to me that the many published scientists that were associated with the CRBPP and knew that false claims had been published in the 1974 journal cloud seeding paper  did nothing.  In that 1974 paper, for example, one reads that the temperature at 490 mb in the atmosphere (about 18,000 feet above sea level) above Wolf Creek Pass, a central target of the CRBPP, was representative of cloud top temperatures during storms.   Both authors, due to the hundreds of rawinsondes launched during CRBPP storms, knew this was untrue.  Robert D. Elliott was one of the two authors.

I  waited years for a correction by the authors, or a journal “Comment” by a knowledgeable, published scientist pointing out that at least this one claim in that article was untrue.  The silence on the part of those many scientists I expected to do SOMETHING was deafening.   I, too,  was part of that “silence.”

Talk Sounds of Silence slide:  a pptx that after hours of investigation I am not able to insert, thanks to changes in WP.  It downloads and then you can play the slide.  In the meantime, this poor substitute for the real thing:

The false claim/misconduct I am referring to appeared in one of the most cited cloud seeding articles of all time, entitled, “The Cloud Seeding Temperature Window.”

Robert D. Elliott, one of the two authors of that 1974 paper was intimate with the CRBPP data as the official evaluator of the CRBPP.  That CRBPP data demonstrated that the claim in his paper that cloud top temperatures over Wolf Creek Pass averaged 490 mb  was false.  In his next visit to Durango I asked him,  “How could you write that (claim)?”   He replied that he had, “just sort of gone along with Lew” (Lewis O. Grant) his co-author.

I thought of Shoeless Joe Jackson and the little kid that said to him, “Tell me it ain’t so, Joe!”, that he had cheated in the Black Sox World Series scandal.  I felt just like that little kid must have.  This was the same Bob Elliott that I had worked for in Goleta  and admired so much.

So, that was the epiphany for me.   I then thought that nothing might be true in the cloud seeding literature no matter how highly regarded that literature or experiment was by the scientific community.

I had come into CRBPP a little too naïve and idealistic, and  when the CRBPP ended, that idealism was nearly gone and replaced by suspicion of any orographic cloud seeding success unless I had personally validated it. Over the next two decades, I was to reanalyze six prior cloud seeding successes in the peer-reviewed literature and not ONE was the success it was deemed to be by the experimenters who conducted it.

This ephiphany set the stage for what was to happen a few years later concerning the scientist in Israel whose work in clouds and cloud seeding Prof. Joanne Malkus Simpson admired so much.

After the CRBPP had ended, I was asked to do an interview about it in November 1975 in the local newspaper, the Durango Herald.   In that interview, I stated exactly what I planned to do; reanalyze all the Colorado State University cloud seeding work that had led to the massive funding of the CRBPP since I now deemed that literature highly unreliable.

After living the winter of 1975-76 in Durango, living off my savings while gathering runoff and CRBPP precipitation data, I was hired for a May-August seeding project in South Dakota by Atmospherics, Inc.  I had worked for them in the summer and fall of 1975  as a radar meteorologist in Madras (now Chennai), Tamil Nadu, India.  While mountain cloud seeding was suspect, Joanne Malkus Simpson and co-authors were published results of successful cloud seeding of tropical Cumulus clouds like those in India.  That’s why I had no qualms about taking that job in India in 1975,  Joanne had influenced me again.

Near the end of the 1976 project in SD, I was interviewed for a job at  the University of Washington by Prof. Larry Radke and Prof. Peter V. Hobbs.  I joined Prof. Hobbs, Cloud Physics Group, as it was known then, in September 1976.

After unraveling bogus cloud seeding successes in Washington State (Hobbs and Rangno 19781 and in Colorado (Rangno 1979, Hobbs and Rangno 19791),  Prof. Peter V. Hobbs who saw I had an interest and skill in examining the cloud seeding literature, said to me that “if you really wanted to have an impact, you should look into the Israeli experiments.”  It wasn’t long before I began reading critically about them.

1Authorship sequences in Prof. Hobbs group, as in these cases, do not reflect who initiated the work, carried out the analyses and wrote the drafts that Prof. Hobbs improved with his great editing skills.



This is a story about Joanne (Malkus) Simpson and our mutual study interest, Prof. Avraham “Abe” Gagin of the Hebrew University of Jerusalem, the leader of the world famed Israeli cloud seeding experiments that took place in the 1960s to 1970s.  This is a story having irony.  For more about Joanne Simpson and her major contributions to meteorology, see J. R. Fleming’s, “First Woman: Joanne Simpson and the Tropical Atmosphere”.  She was a real superstar.


My own modest claim to fame,  partly for the work reported here:…/two-uw-researchers-honored-by-un-for-excellence-in-weather-modification

Following the untimely passing of Professor Abe Gagin[1], Joanne Simpson stated that, “statues will be raised in many towns and halls of fame” in his memory due to his contributions to cloud seeding. Her testimonial appeared in the 1988 memorial issue to A. Gagin of the J. Weather Modification and is shown at the end of this account.  The memorial issue of that journal is here:


As a measure of Prof. Gagin’s stature when he passed and why statue building might be considered for him, the October 1989 J. of Appl. Meteor. also issued a memorial volume to Prof. Gagin in due to his work in cloud seeding.  The preface to that memorial issue, written by Arnett S. Dennis, a former co-author of Joanne’s, is also shown at the end of this account.  Hardly any scientists are tributed by memorial issues of journals, much less, two!  Prof. Gagin’s frequent co-author in describing the results of the Israeli cloud seeding experiments, Prof. Jehuda Neumann, was ALSO tributed with a memorial issue of the J. Appl. Meteor. when he passed ten years later.

Prof. Gagin passed in September 1987 at the untimely age of 54, a few months after learning in a letter from Prof. Peter Hobbs that my manuscript, “Rain from clouds with tops warmer than -10°C in Israel,” had been accepted for publication by the Quart. J. Roy. Meteor. Soc.  This paper showed that the clouds of Israel were completely different than the ones Prof. Gagin was repeatedly describing in the literature and at conference.

At the same time of his passing, Prof. Gagin was also being pressured by his own chief meteorologist, Mr. Karl Rosner, to publish the previously omitted data for the south target of Israel-2.  This was the 2nd randomized cloud seeding experiment that was conducted from the 1969/70 through 1974/75 Israeli rain seasons.  The reporting of Israel-2 had been confined to the north target where there was an appearance that cloud there had pretty much replicated what had been reported in ALL of Israel-1.

The testimonials to A. Gagin by many leading scientists in the cloud seeding domain were omitted in the digital version of the 1988 JWM volume when digitizing  was done many years later but can be found at the end of this story.

My one and only in-person interaction with Joanne Malkus Simpson:  “Go into journalism not meteorology.”

I met with Joanne (Malkus) Simpson in January 1963 at UCLA.  She had been brought to my attention when she had been named, Los Angeles Times “Woman of the Year.”  I was meeting with her, a professor of meteorology, to try and convince her that as a 20-year old junior college student, I was worthy of getting into the UCLA meteorology program even though I did not have a high enough grade point average to do so.  UCLA required a minimum of 2.4 and mine was barely above 2.0000x.  And I had to repeat all but one of my calculus and physics classes at Pierce Junior College.  I had spent too much time playing and practicing for intercollegiate baseball, but I also had no natural aptitude for physics and calculus.

UCLA was the only school offering courses for a degree in meteorology in California in 1963, and that’s why I went there to meet with Dr. Malkus, as she was known as then.  It seemed like UCLA offered the only hope of achieving my dream to become a meteorologist.   I thought explaining my fanaticism about weather would do the trick.  For example I had gone to Louisiana and ended up near Galveston, Texas, chasing Hurricane Carla in September 1961, and chased numerous thunderstorms in the Southern California desert during the summers.

Some early background that if told to Joanne, would convince her I was worthy of UCLA’s program

I began collecting weather maps out of the Los Angeles Daily News when I was in the 4th grade.  (Thank you, Mr. Borders and Mr. De la Gega, my 4th and 5th grade teachers, for encouraging my budding interest!).  Below a sample of a real weather map with isobars from the Los Angeles Daily News for December 26, 1951.  How exciting is this?

Too, I was subscribing to the “Daily Weather Map” by the time I was ten years old.   By the time I was 13 years old, I  was subscribing to the Monthly Weather Review and several states’ government, “Climatological Data” from NOAA.   (Well, my mom subscribed for me.)

I crazily thought that telling Joanne about all this would get me in to UCLA sans the grade requirement.

“The Meeting”

The first thing Joanne Malkus asked me when she kindly took a minute out of her busy schedule (I had made no appointment) was how my grades were in math and physics.   I told her I got “Cs” but did not reveal to her that those “Cs” were on the second try!   She then asked me, “How are your grades in the humanities?” “B’s.”   With my answers to but two questions, Prof. Malkus then advised me to give up the thought of becoming a meteorologist, and become, perhaps,, “a journalist and write about weather.”  And that was the end of the meeting; in less than five minutes I was advised to give up a life-long dream.

Yes, I “held myself back,” to repeat courses in math and physics, and in doing so lost my collegiate baseball eligibility.  Who would do this?But.. that stubbornness, to keep at it, not giving up  my dream, turned out to be key to my whole life.  But perhaps it could be seen as a character flaw, too?

Joanne Malkus assessment of my potential as a student in the UCLA meteorology program was, in fact, “spot on.”

Thank you, Joanne (Malkus) Simpson.


In retrospect, I never could have gotten through the highly theoretical program at UCLA in those days, a program that featured Morton Wurtele, Yale Mintz, Morris Neiburger, Jörgen Holmboe, Zdenek Sekera, James Edinger, and Jacob Bjerknes, the latter who had founded the Department in 1940.  Fjørtoft, a visiting Norwegian professor of meteorology, or possibly Holmboe, was slinging vector equations across a blackboard as I walked down the hall following my meeting with Prof.  Malkus.  At UCLA in those days, one would have walked the halls with giants. A few years earlier I had tried to get the autograph of Prof. Bjerknes at UCLA since meteorologists like him were to me,  like baseball superstars to other, “normal” kids.  Prof. Bjerknes was not in his office that day, but rather there was a sign said he was, “emeritus,” which I took to mean he was especially good as a scientist, not that he was retired.

After my 1963 meeting with Joanne Malkus I was angry and hurt and promptly went to the UCLA bookstore and bought one of the books they were using in their meteorology program, I was that mad.  The book?  “Introduction to Theoretical Meteorology” by Seymour Hess.  I stopped reading it after a day or two.  It had too many equations. 

It took me more than 25 years to realize that Joanne Malkus Simpson had saved me from myself.   I wrote her a note thanking her  for her keen assessment in the early 1990s.   She did not reply.  

Life After “The Meeting”

In  the spring of 1963 I had lucked out and gotten a job as a “research analyst” at Rocketdyne in their H-1 rocket group in the Simi Hills above the San Fernando Valley.  Rocketdyne was a division of North American Aviation.  By mid-1964, I was “suddenly” married and had a son.  Becoming a meteorologist was slowly slipping off the radar, but I loved my job at Rocketdyne (about Rocketdyne)  and the young, great engineers that led my group, like Wayne Littles  who later became the 8th director of the NASA Marshall Space Flight Center in Huntsville.  They set great examples as engineers and leaders.

Rocketdyne’s Simi Hills test division where I worked, had a weather forecast office and I bugged the guys there, Joe Glantz (former State Climatologist for California) and Hank Weiss, virtually EVERY lunch time during the winter rain season.  We talked “progs” such as they were then.

I also started on another path toward being a meteorologist while married, still not giving up on my goal.  I took two correspondence courses in meteorology from Penn State University (graded by A. K. Blackadar and F. B. Stephens).

When my marriage was going on the rocks in the mid -1960s due to my immaturity, I learned that San José State College had started a program in meteorology.  I applied and got accepted even with my crummy grade point average from junior college.  It was an exciting time for me to meet, for the first time in my life, other weather-centric guys like me when I arrived at SJS in the spring of 1967.  One of them, Bill Hall, was to become something of a modeling superstar at the National Center for Atmospheric Research.  Byron Marler, who ended up with PG&E,  became a life long friend.

I also became friends with the chair of the Meteorology Department in those days, Dr. Albert Miller.  He helped me tremendously by hiring me as a student assistant while I was an undergraduate, and later, as a graduate assistant in the synoptic lab.  Dr. Miller was like a 2nd dad to me.  Also key to being able to continue at San Jose State  was my former Rocketdyne supervisor, A. Dan Lucci, who re-hired me as a summer employee at Rocketdyne in 1967 after my first semester at San Jose State.

Another person whom I became good friends with at SJS due to working together, was C. Donald Ahrens, who was to go on and write the most popular meteorology book for 101 college classes in the nation, “Meteorology Today” and several other books.    His wife was to type the first chapter of his Meteorology Today book on my very own Hermes 3000 manual typewriter!

Don and I also worked together on tetroon (constant level balloon) paths in the Bay Area that disclosed where the onshore maritime air was going.  We worked in a corrugated metal building next to the football stadium far from the meteorology department.  To pass the otherwise tedious time, we had KGO-FM’s no commercials, top 40 radio station with DJ “Brother John” blaring.  And, we would break into song!  We really liked the Four Seasons, Western Union, by the Five Americans, and so many others that  we sang to many of them, harmonizing,  while our heads were down plotting tetroon paths.  I still smile thinking of those days.

In the summer of 1968, I worked for non-other than North American Weather Consultants under CEO, Robert D. Elliott.  That  summer Tor Bergeron came to visit!  For those readers who remember NAWC in Goleta, California, here’s the photo I took of the whole gang, Elliott, Bergeron, Keith Brown, Russ and Elona Shaefer, John Walter and others whose names I  can’t bring to the “surface:”

I’ve never had a job I loved as much as that summer one at NAWC, or people I had so much in common with there.   I also had a chance to meet the head of NAWC, the famous Robert D. Elliott, whom I came to admire so much while at NAWC.  My assignment at NAWC was mainly to draw weather maps of frontal systems coming into southern California and “lake effects” for the Great Salt Lake in winter.  I was in heaven.

Back at San Jose State in the fall of 1968, I started a tiny forecast blurb on the front page of the Spartan Daily.  It devolved into political satire at the suggestion of the Daily’s editor after one my forecasts, “…with the stratus, not the campus, burning off by noon.”  There had been some fires set in trash cans by protestors the day before on the San Jose State campus.   The Daily editor said I should do more of that, and off I went into some pretty lame stuff.  Oh, well; “let’s move along now, nothing to see here.”

I also began to write opinion pieces in the San Jose State Daily, mostly due to the encouragement of Prof.  Phil Wander, my speech teacher.  I deem him one of the most important influences in my life. He thought I had something to say, such as this from a talk I gave in his class:

I was also writing articles for the college paper on ending student funding of intercollegiate athletics due to Governor Reagan’s budget cuts, pollution and the effects on minorities (above), suggesting parking costs be based on the number of people in the car, and on the war in Vietnam, the latter as many others were.  My SJS experience is pretty much reprised in the “friendly” article below, miniaturized for the sake of humility, of which, I probably don’t have enough of:

I graduated from modest San José State College, as it was known then, with a Bachelor of Arts degree in meteorology in January 1969.   My grades, for so much effort I put into my meteorology classes with lots of math were,  nevertheless, mostly mediocre except in synoptic classes.  However,  I was a good weather map drawer and getting A’s in synoptic classes really helped raise my grade point average.

Perhaps due to writing topical articles in the SJS Spartan Daily,   I received the Meteorology Department’s Achievement Award when I graduated in January 1969.  Egad.   I was never sure I deserved it with big hitters and great students like future NCAR cloud modeler, Bill Hall, and other top students like Norm Hoffman, Chris Fontana, in my class getting “A’s.”

An example of over valuing my satirical talent that were on display in the Spartan Daily weather forecasts,  in the summer of 1969, I went to KRLA-AM in Los Angeles to suggest that I could be a weather forecaster for them.  KRLA was a top 40 station whose news team suddenly began doing news satire in 1968, and they dared to offend.   What they did was astounding to me and was even noted in Time magazine!

I wondered if I could be their weather forecaster, and maybe chip in to the their comedy team,  later called,  “The Credibility Gap”.  I showed a page of my Spartan Daily forecasts to a young Harry Shearer, a member of the KRLA satirical news team.  He quickly glanced across them and summarized his thoughts on them like this; “They’re not that funny, are they?”  End of interview.

I hung around San Jose State attending graduate classes until the spring of 1970.   At that time I was offered a job as an assistant weather forecaster with the nation’s largest ever randomized mountain cloud seeding experiment headquartered in Durango, CO,.  Funded by the Bureau of Reclamation, it was called the Colorado River Basin Pilot Project (CRBPP).   I was hired after being interviewed by J. Owen Rhea of E. G. & G, Inc.  in San Jose!  E. G. & G., Inc. had just been selected over North American Weather Consultants (NAWC) as the seeding contractor for the CRBPP.  Owen was going to be the lead forecaster under Paul T. Willis, the E. G. & G., Inc., Project Manager.

I really didn’t belong in grad school, either; too many equations.  Nevertheless,  it was hard to leave the excitement of SJS of those days.  SJS track stars, Tommy Smith and John Carlos had just drawn national attention to SJS,  that season’s NCAA track champion,  at the 1968 Olympics in Mexico City with their raised, “black power” fists.

I also received a job offer from NAWC in Goleta, CA, at that time, too.  I did not know until decades later that they were finalists in bidding on the same contract that E. G. & G., Inc. had won from the Bureau of Reclamation for the seeding and forecasting operations for the Colorado River Basin Pilot Project.

But the job in Durango seemed so important and exciting; I was going to be a part of a giant scientific experiment to see if cloud seeding worked and so that’s where I went.  The thought that it was exciting that I would also be living in a new climate after a lifetime in California’s.

1970:  It was now seven years since Joanne had advised me to give up the idea of being a meteorologist.  And now I was going to enter a field that she was a top expert in; weather modification by cloud seeding.



(Joanne Malkus/Simpson and Abe Gagin)

A modern-day story with elements similar to that of American physicist R. W. Wood and his exposé of non-existent “N-Ray” radiation in 1904.  R. W. Wood went to France to expose “N-rays” as the product of experimenter delusion at the turn of the century (Broad and Wade 1982); our protagonist1 went to Israel in 1986 to expose faulty cloud reports by possibly deluded scientists.

The underlying message in this life story chapter?

Hold on Tight to Your Dreams“, one of the greatest-ever song messages.  You just might make something out of yourself even when it appears you don’t have the grey matter to do it, as in my case (the “protagonist” in the outline below.)  “EOM”–skip the rest if busy.

Story board

  • A young, “weather centric” student in junior college, the protagonist in this story, meets with Prof. Joanne Malkus, a famous woman scientist and faculty member at UCLA in meteorology in 1963. He is there because her university is the only one in his state of California that offers courses leading to a degree in meteorology.   She has come to his attention because she had just been named, Los Angeles Times “Woman of the Year.”
  • Though he has loved clouds, weather and forecasting since he was a little kid, he tells her he is struggling in junior college with the courses that future meteorologists are required to take, ones heavy in calculus and physics, and doesn’t have the grade point average to get into UCLA from junior college.  He is hoping to convince her he is worthy of a shot in their meteorology program anyway due to his enthusiasm about becoming a meteorologist.
  • Malkus, after hearing about our protagonist’s poor grades in math and physics, suggests it would be best for him to give up his dream of being a meteorologist and to go into something less rigorous, perhaps “go into journalism and write about weather.”
  • Eventually, and holding himself back by repeating courses in math and physics to get “C’s,”  the stubborn young man becomes a meteorologist, anyway, matriculating at San Jose State College, one that starts a meteorology program a few years after his 1963 visit to UCLA.
  • By chance, our protagonist eventually ends up being an expert in the same specialty as Prof. Malkus (now Joanne Simpson) whom he had met with many years earlier;  rainmaking by cloud seeding and Cumulus cloud structure at the University of Washington under Prof. Peter V. Hobbs.
  • Simpson is particularly enamored of the work of a leading rainmaking scientist in Israel, Prof. Abe Gagin. When Prof. Gagin passes in 1987 at the age of 54,  she proclaims that, “…statues will be raised in many towns and halls of fame to his memory.”  Her view about that rainmaker is shared by many others around the world.
  • Through the rigorous execution of two well designed rainmaking experiments in Israel, each with similar increases in rain, in turn supported by repeated descriptions of Cumulus clouds plump with rainmaking potential, the experiments in Israel, by the 1980s, are deemed to be the one true rainmaking success in the world among all those undertaken.


  • Our protagonist, who on his own initiative, has exposed mistaken or fraudulent claims of “successes” in the peer-reviewed rainmaking literature since the late 1970s, comes to doubt the validity of the published work of that very same scientist for whom “statues will be raised.”
  • In the late 1970s after exposing ersatz seeding successes in Colorado and Washington State, our protagonist’s lab chief, Prof. Peter V. Hobbs, challenges our protagonist, a mere staff member in his group, to investigate the famous experiments in Israel, advising him, “if he wanted to have a greater impact” in his specialty of unraveling false cloud seeding claims.
  • Our protagonist begins to do so, and supplies a list of questions, at the request of Prof. Hobbs, to ask Prof. Gagin about his experiments when Prof. Gagin reports on them at a 1980 international conference in France.
  • In 1983, while Prof. Hobbs is on sabbatical in Europe, our protagonist submits a paper to a journal that asserts that the clouds in Israel are not ripe for rainmaking, but rather quite the opposite, and that too little seeding was carried out in the Israel-1 cloud seeding experiment was not enough to have affected rainfall.  Israel-1 was the first of the two famous experiments.
  • The paper is rejected by three of four reviewers. One of the “reject” reviewers he later learns, is Prof. Gagin himself.
  • Our protagonist is undaunted by the rejection of his paper, and begins to contemplate going to Israel after he also reads about American physicist, R. W. Woods’ trip to France to expose N-Rays.
  • Our protagonist resigns at the end of 1985 from the job he has loved over credit issues with Prof. Hobbs and goes to Israel on 4 January 1986.
  • Prof. Hobbs is not onboard with our protagonist’s views on the clouds of Israel before he leaves. He describes our protagonist as “arrogant” for thinking he knows more about the clouds in Israel than those “who have studied them in their own backyard.”
  • Our protagonist eventually exposes the famed rainmaker’s faulty work on several fronts beginning with his self-initiated and self-funded cloud investigation to Israel in 1986, a science excursion that resembles the historic trip by R. W. Wood to France. During the first storm in Israel he finds that the cloud descriptions by Prof. Gagin are, indeed, in error.


  • Our protagonist is welcomed by the Israel Meteorological Service (IMS) and given a tiny amount of desk space where he collects historical  data concerning Israel’s clouds and rains, data that will be used in a journal paper.


  • Not surprisingly, he finds that all the IMS forecasters know that it rains from clouds that are contrary to those described by Prof. Gagin’s descriptions in the journal literature.  They are much shallower than those described as necessary to develop rain by Prof. Gagin, making them appear necessary for seeding to take place to make them rain.


  • Following a first cordial meeting at Prof. Gagin’s office following a week of dry weather,  a second meeting occurs after several days with rain. Our protagonist discusses his observations with Prof. Gagin, which are sharply at odds with his journal cloud descriptions of Israeli clouds.  Gagin, understandably at the end of our protagonist’s discussion, asks him to leave and never come back; “do your own thing.”


  • Despite what happened in the second meeting, a third and final meeting is arranged with Prof. Gagin on 2 February 1986.    It occurs at the offices of his  rainmaking headquarters on the grounds of Ben Gurion International Airport.  Our protagonist asks if he can visit this headquarters to observe radar cloud top heights during storms.  His request is declined by Prof. Gagin, who insists that his cloud descriptions are correct.


  • In  mid-February 1986 our protagonist meets with the “Chief Meteorologist” of the Israeli cloud seeding experiments, Mr. Karl Rosner. He is informed by Mr. Rosner that a large amount of data was omitted in the reporting of the 2nd “confirmatory” rainmaking experiment whose results were published in 1981.  As it was published without that data, Israel-2 appeared to be a strong confirmation of the results of Israel-1 in the eyes of the world. Mr. Rosner, he tells our protagonist,  is now trying to get Prof. Gagin to publish the missing data.


  • The weather fails to deliver any more significant storms through 10 March, and our protagonist departs Israel after 11 weeks of cloud studies and data thanks to the IMS.


  • In June 1986, in a letter to Prof. Gagin, our protagonist summarizes his cloud findings; his letter is copied to several leading scientists. In this letter, our protagonist vows that he will leave the field of meteorology altogether if his observations concerning the clouds of Israel are wrong; that high concentrations of ice crystals occur in clouds with tops >-12°C. He challenges Prof. Gagin to leave the field if he is right.
  • Gagin, just 54 years old, passes in 1987 a few months after being notified in a letter by Prof. Hobbs that our protagonist’s cloud investigation has been accepted for publication in the Quart J. Roy. Meteor. Soc.
  • Two journals issue separate memorial issues to Prof. Gagin’s memory in 1988 and 1989, an exceptionally rare tribute that testifies to his standing. Joanne Simpson’s testimonial to Abe Gagin is published along with several others in the 1988 issue of the J. Wea. Mod.
  • The results of our protagonist’s cloud investigation are also published in 1988. It concludes that the clouds aren’t plump with cloud seeding potential as they have been repeatedly described by Prof. Gagin, but are quite the opposite of those descriptions, repeating the conclusions in his rejected 1983 journal submission to the J. Appl. Meteor.  The paper questions how cloud seeding could be effective given the actual nature of Israel’s precipitating clouds.
  • Like N-rays, it is eventually it is revealed in multiple reports that the clouds ripe with rainmaking potential that were described by Prof. Gagin do not exist.
  • 1990: the “full” results of the Israel-2 cloud seeding experiment are reported as urged by Mr. Rosner.  It is now found that the “full” Israel-2 experiment, incorporating previously omitted data, had a null result contravening the previous view of Israel-2 as unambiguous rainmaking success.
  • However, it was also hypothesized in the 1990 journal article that there could have been increases and decreases in rain separately in each of the two targets in Israel-2.   Thus, when these differing results were combined as the design of Israel-2 called for, they canceled each other out, thus causing the null result of the whole experiment and leaving an enigma.
  • 1992: Our protagonist’s 1988 cloud reports are first corroborated in airborne measurements by Tel Aviv University scientists unaffiliated with seeding activities. The Israeli clouds, indeed, appear to have little rainmaking potential due to having high concentrations (10s to hundreds per liter) of natural ice crystals in them at cloud top temperatures >-13°C.  These airborne reports are reiterated in separate publications in 1994 and in 1996.  More research supporting our protagonist’s cloud investigation appears over the next 20 years.
  • 1992: a journal paper by the promoters of rainmaking, one a protégé of Prof. Gagin, claim that dust interfered with Israel-2; that actual increases in rain occurred when there was no dust and decreases in rain occurred when there was dust.   Thus, a “dust hypothesis” is put forth to explain possible real increases and decreases in rain that were suggested in the full result of the 2nd experiment in the north and south targets.


  • Joanne Simpson, who advised our protagonist to give up the thought of being a meteorologist, finds the “dust hypothesis” highly credible. Our protagonist and Prof.  Simpson are now on a collision course in opinions again.


  • Our protagonist finds the 1992 dust claim ludicrous due to his 11-week cloud investigation in Israel in 1986.  He decides that something must be done about the dust claim.  He begins working at home on his own time in 1992 on the daunting task of reanalyzing Israel-1 and Israel-2.
  • Our protagonist’s reanalyses of the two statistical experiments in Israel are published in 1995 in the J. Appl. Meteor.  Prof. Hobbs is a co-author.  The reanalyses conclude that rainmaking activities did not increase rain in either Israel-1 or in Israel-2.  The clouds are also shown to form precipitation rapidly, leaving little opportunity for rainmaking.
  • 1997: Critical commentaries of the 1995 paper are published. The number of pages of criticism of the 1995 paper sets a record for the pages of  “Comments” on a paper ever published in an Amer. Meteor Soc. journal.  An ox has been gored.  In effect, our protagonist and Prof. Hobbs have become the most “criticized” meteorologists in the history of the Amer. Meteor. Soc.
  • However, the 1995 reanalyses and the 1997 journal exchanges trigger the first major independent review of rainmaking in Israel by the Israel National Water Authority (INWA). This organization had previously relied on the reports of the rainmaking promoters and other rainmaking partisans that rainmaking was working to increase runoff into the country’s largest freshwater lake, the Sea of Galilee, aka, Lake Kinneret.


  • 1998:  The results of 19 winter seasons of randomized cloud seeding in Israel-3 in the southern part of Israel are reported. There has been no effect on rainfall due to seeding.  The results again indicate that the clouds of Israel are unsuitable for cloud seeding.


  • 2006: After several years of study, the independent Israeli review panel reports that they can find no viable evidence that rainfall has been increased in 27 years of rainmaking (1975-2002)  targeting the Sea of Galilee  watersheds.
  • The independent panel’s finding corroborates the conclusions in the 1995 reanalyses by our protagonist and Prof. Hobbs, and supports the findings of our protagonist’s cloud investigation published in 1988: the clouds in Israel are not viable for rainmaking.
  • Once again, this rainmaking story seems to have reached a conclusion when rainmaking  is terminated in 2007 or 2013.      But it is not so.
  • The promoters of rainmaking in Israel argue that air pollution has suddenly canceled increases in rain due to rainmaking activities during the last decade of the program .  They argue that the review panel’s findings of no viable increases in rain are faulty because they do not include air pollution effects.
  • The independent review panel, and several other scientists in Israel find the air pollution argument by the promoters of rainmaking unconvincing and cloud seeding of the Sea of Galilee watersheds does not resume.
  • In 2010  Tel Aviv University scientists find that the supposed rain increases in the Israel-2’s north target days lacking in “dust,” were bogus. The seeding partisans had been misled in their conclusion because stronger storms happened on days when rainmaking took place in the “dust-free” target.
  • Once again, the story seems to have reached a conclusion in 2010 due to the new independent reanalysis described above. But again, it is not so.
  • 2012: The Israel National Water Authority is convinced to try once again to see if rain can be increased by cloud seeding in a new, sophisticated, randomized experiment, Israel-4.  This time the experiment targets the mountainous, northern extremity of Israel.
  • The conduct of a new experiment is supported by airborne reports by the rainmaking partisans who conclude that the clouds have a lot of rainmaking potential in northern Israel.
  • Importantly, instead of being carried out by seeding partisans, the new experiment is carried out by independent Israeli scientists.
  • Israel-4 ends in 2020 after seven winter seasons. There is no indication that a viable amount of rain has been increased by rainmaking.   The official null “primary” result has since been published by Benjamini et al. 2023, J. Appl. Meteor.
  • This result of Israel-4 parallels the several prior conclusions by external skeptics concerning all the rainmaking activities in Israel, including those by our protagonist and Prof. Hobbs concerning Israel-1 and -2.
  • The null results of Israel-4 experiment also reiterate those of our protagonist in 1988 concerning the clouds of Israel; they are not conducive to rainmaking.
  • This time, in 2023, our “story” finally seems to have reached an end.
  • But how can the “story” end?  Think of the courage it would take for those who promoted seeding in Israel for so many decades and who have cost their own country so much in wasted seeding programs to walk away from repeated faulty analyses and descriptions of non-existent, ripe for seeding clouds?  They won’t.  Count on it!

1Art and Prof.  Peter V. Hobbs, the Director of his group,  were honored by the UN partly for the work reported here.  The 2005 monetary prize was adjudicated by the World Meteorological Organization.

If anyone has gotten this far, you can go even deeper in these posts:

Chapter 1: My One and Only Meeting with Joanne Malkus/Simpson

Chapter 2:   A Story About Lost  Idealism Concerning Science that Leads Eventually to Israel

Chapter 3: The Review of the Israeli Cloud Seeding Literature Begins

Chapter 4:  The Trip to Israel to See the Ripe for Cloud Seeding Clouds that I Doubt Exist

Chapter 5, the last:  Got Published!