All posts by Art Rangno

The Myth: Climate scientists were not on the global cooling bandwagon in the 1970s

Advisory:  heavy reading ahead…have to fill time during current cloud drought

In an article published in the Bulletin of the American Meteorological Society (BAMS) in 2008, it was asserted that there was no “concensus” on global cooling in the 1970s.  Why address this now?  I was busy before now….

Overall response to this BAMS assertion:

Hogwash!  Rubbish!  Bilge!  (I’m pretty “excited” here).

In fact, perhaps the most outrageous statement I have ever seen in a peer-reviewed journal was that of the BAMS Editor, quoted below in red.  In defense of the Editor, he was only parroting the conclusions of a major article in that BAMS issue purporting this distortion.  The appearance of such an article can be seen as a failure of peer review.   Here is what the BAMS Editor wrote in summarizing that bogus claim:

“In this issue, (the authors-names omitted) show that we were indeed misled about global cooling–but not by scientists. (emphasis added by the present writer).   Rather, we are confused about the recent history of our own science.”

I wanted to gag when I read this.  I was doing decadal climate studies in the early 1970s and so I was “pretty familiar” with the literature.

First of all, what were scientists really saying about climate change back then?  I will cite two major sources from the 1970s:

Below, a quote by Wilmot N. Hess, then the Director of 11 NOAA programs,  from the preface of  Chapter F on Climatic Change in the book, Weather and Climate Modification, published by Wiley Interscience in 1974.  (The volume, a collection of essays by experts,  targeted senior-level college students in the sciences and engineering, or working scientists or engineers who don’t know much meteorology.)

“It has been suggested recently that we are near the end of an integlacial period.  Studies of climate changes are in their infancy.  We know that there have been four episodes of glaciation in the recent past covering a period of about 1,000, 000 years.  A conference at Brown University in January 1972 discussed this problem and the MAJORITY (the font can’t be big enough here!) of the participants concluded that:

Warm intervals like the present one have been short-lived and the natural end of our warm eposch is undoubtedly near when considered on a geological time scale.   Global cooling and related rapid changes of environment, substantially exceeding the fluctuations experienced by man in historical times must be expected within the next few millenia or even centuries.‘”

Here’s what those climate scientists were looking at over just the past 100, 000 years of the earth’s climate.   Their concern will be obvious.  Note the “present” is on the left, not right as per normal.  The numbers “4” and “5” represent “interglacial” warm periods, the first the present one, called the Holocene, and “5”, the Eemian interglacial period.  Look, too,  how the temperature was trending DOWNWARD over all that glacial time until our present interglacial.  Source:  National Academy of Sciences, 1975.

Now imagine you are a journalist at that Brown University Conference…and you also learn that the earth’s temperature has been falling for more than 25 years (not shown in the above graph).  Futhermore, the CO2 people also inform you that the recent decline in temperatures over that 25 years would even be GREATER if it wasn’t for the mitigating effect of CO2!

What are you going to tell your public?   It’s obvious.

So how did such a scientific distortion get published in BAMS in 2008 by supposedly knowledgeable authors? Were they themselves confused about the history of climate change?  Was it due to their methodology?  Or was it a propaganda piece all along, a revisionist history resembling something analogous to the type of pieces that came out of Pravda of the former Soviet Union, a piece written to correct an earlier error,  so that that we scientists look like we had it right all along?  Probably all of these, in this writer’s opinion.

Lets look at what the authors did.   The full article is here.  In support of their phony claim, the authors of the BAMS article used a “bean counting” approach, the results of which they display in a contingency table.   They tabulated articles on climate change and its likely causes in peer-reviewed journals, looked at the conclusions, and if the article concluded that CO2 was going to warm the world, it would be placed in the warming world column, if the conclusion was ambiguous they gave it a nul ranking, and if the article concluded we were headed for a cooling, it went into that column.  The authors then told us that because they were more articles about CO2 and warming than nul or cooling articles, that must be what everyone believed, a major fallacy in reasoning.

However, either out of ignorance of our science hierarchy,  or having an axe to grind, they counted prestigious reviews with the same as that assigned to a single publication by “Joe Blow”, somebody who might never have been heard from again.   So when they counted an 1975 assessment by the National Academy of Sciences, an organization that periodically reviews subjects of critical interest, employing dozens of experts and reviewing dozens of peer-0revied articles, the authors assigned that review the same weight as the other publications.   It was like assigning an elephant the weight of a flea.

Nor did the authors mention the 1968 American Meteorological Monograph, The Causes of Climatic Change; not ONE paper in that tome discusses CO2 and its possible effect on climate!

And, of course, they did not cite the Wiley-Interscience volume with its contents concerning climate,  quoted above.

But why were scientists in the 1970s concerned with global cooling and not paying so much attention to CO2?

By 1975, the earth’s temperature had been in DECLINE for about 30 years!   This was in spite of massive increases in CO2 during that 30 years.   The cause of that decline has not been ascertained even as of today.  That decline in temperatures was reversed in the late 1970s,  as has the cause of the leveling of the earth’s temperature during the past 10-12 years, also in spite of increasing CO2.  Furthermore, some authors attributed that reversal to changes in the Pacific Decadal Oscillation which occurred in the late 1970s, not to CO2.

Against that background of a long term decline in temperature by the mid-1970s, it was known that the current “interglacial” period we are in (also known in science-speak as the “Holocene”)  would not last forever.   In fact, it had gone on about as long as the earlier one about 100, 000 years ago, called the Eemian (number “5” in the figure above), or about 10-12,000 years.  This was of concern to paleoclimatologists in the mid-1970s against the backdrop of declining temperatures.   Recall we departed from ice age conditions in fits and starts only about 18,000 years ago, and after a few thousand years reached the current Holocene “warmth.”

Here’s what the National Academy of Sciences (Understanding Climatic Change) had to say in 1975, p188:

“One may still ask the question:  When will the present interglacial end?  Few paleoclimatologists would dispute that the prominent warm periods (or interglacials) that have followed each of the terminations of the major glaciations  have had durations of 10,000 +-2,000 years.  In each case, a period of considerably colder climate has followed immediately after the interglacial interval.  Since about 10,000 years has elapsed since the onset of the present period of prominent warmth, the question naturally arises as to whether we are indeed on the brink of a period of colder climate.   Kukla and Mathews (1972) have already called attention to such a possiblity.  There seems little doubt that the present period of unusual warmth will (emphasis in the original) eventually give way to a time of colder climate, but there is no consensus with regard to either the magnitude or the rapidity of the transition.  The onset of this climatic decline could be several thousand years in the future, although there is a finite probability that a serious worldwide cooling could befall the earth within the next hundred years.”

So, global cooling is in our future, no doubt about it.  However, the NAS pointed out that the bad for us cooling might be offset by CO2, or, if there was a further warming, that before the eventual cooling, that CO2 would exacerbate that.  To me, what was being written by the NAS was vastly different than the mere “0” assigned to that piece by the BAMS authors.

Now, when a journalist reads a statement by the prestigious National Academy of Sciences that there is a possibility of a “climatic decline” (that’s how cooling was looked at, namely, it would be worse weather for us than we have now in the Interglacial) in just a hundred years, what is he going to write?  If he wrote about that for, say,  Time magazine, that global cooling was “in the bag” and might even happen within a 100 years,  he would have gotten it  from our highest scientific organization.

In sum, there WAS widespread concern among climatologists and scientists about global cooling, particular in the early 1970s.   It was no myth.

 

 

Climate change: What they were saying, 1968

While waiting amid the smoky skies for some clouds…

In 1968, the American Meteorological Society (AMS) published a Monograph, Volume 8, No. 30, to be exact.   Monographs are special collections of papers on a particular subject representing experts in the field and their purpose is to bring the scientific community up to date on the progress in that field.  This particular monograph was entitled, The Causes of Climatic Change. The Editor of this collection was J. Murray Mitchell, a world renown climate expert.  There were 18 papers by various experts in the field of climate.  Not ONE of those papers addressed the influence of carbon dioxide!

Only in the concluding remarks, does J. Murray Mitchell mention that we have to keep an eye on CO2 because it still may rear its head in modifying climate.

Why was there not a single paper on CO2 in that 1968 AMS volume on climate change?

There were papers being published in journals about the possible influence of CO2 on climate.  However, while CO2 was increasing drastically during the 20th Century, the global temperature had begun  declining slightly for about 20-25 years (from the early 1940s) when this monograph was published.   So, while it was known that CO2 COULD warm the climate, something else was going on in those days even as CO2 increased.

Most troubling in the context of falling global temperatures, as Mitchell points out in his concluding remarks, is that the causes of ice ages were not understood.  Several theories were put forth in this volume, such as  “galactic dust” having reduced solar radiation, but none were satisfactory in those days.

SO with the earth’s temperature in decline, it is not surprising that CO2 was “off the radar”, or very distant at that time, and with a cooling underway, that theories about the causes of ice ages seemed to be more important.

That situation was not much changed into the mid-1970s where in the National Academy assessment of Climate and Weather Modification:  Problems and Progress, we find the NAS panel noting the “recent equatorward shift in ice boundaries.”

Cirrus show

Just a couple of photos of yesterday morning’s glorious display of Cirrus (OK, “uncinus”) clouds, those high, icy white ones that were so fantastic enhanncing the desert and Catalina mountain background, taken from on top of a horse.

As you know by now, those Cirrus clouds are composed of tiny ice crystals, but, as tiny as they are, they are generally far larger than droplets in clouds.  So,  when ice clouds form, they are essentially precipitating clouds.  Those ice crystals are too heavy to stay aloft and the larger ones settle out producing these extremely fine, delicate strands.  Sometimes those trails extend thousands of feet below the “head” of the cloud where they were generated, and as they fall, go into regions where the wind is slightly different in velocity and direction, and so you get interesting twists and turns.

If you could fly up there, you would find tiny snowstorms of simple ice crystals shaped like little bullets (a crystal type), triangular prisms, stubby columns,  or plates, crystals that would  sparkle as they went buy and showed their pristine faces to the sun.   Seen’em do that many times when with the U of WA and their flight research program.  They look like daytime shooting stars, or fairy dust, as they rush by the pilot’s window,  and also where I was, viewing from a dome atop the fuselage of our various aircraft.  You would not know you were in a “cloud” except for those displays.

The last photo is of a droplet cloud, Cirrocumulus, composed of extra tiny cloudlets.   It was a higher altitude one, pretty cold up there, maybe -30 C.   Went off the “screen” before it may have crystalized into a Cirrus cloud many do. I thought it was a nice view, taken on the Canyon Loop Trail near Green Rock yesterday.

The End.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Altostratus: before and after (being underlit)

In the first shot here, you’re getting pretty excited.   There are holes in the mostly icy Altostratus translucidus deck, your camera is charged up for plenty of shots, because with the holes, and,  with the satellite imagery indicating a western edge of these clouds over central AZ, you realize this whole scene below will be INFLAMED with color before long.   But you have an agenda:

You’re thinking of sending another round of glorious, unforgettable, studpendous sunset pictures to your friends in, say, Seattle, Washington,  where it has been overcast and cold ALL day.  Also, it seems that March through May has been the coldest in 55 years there.  You feel bad for them, but not THAT bad.

Your new photos will help them realize the mistake they made by not moving to Arizona and joining you here in a new life.  They will feel bad again.  But, you refrain from “enabling” them  in the consequences of their decisions by saying weather platitudes like,  “I could use some of your overcast skies everyday and cold air here!  Its about 100 F here today, just awful.”

Of course, with the low humidity hereabouts, its not awful at all.  In fact, you drive around with your windows down to show how not awful it is.   Still,  you want THEM to feel that little bit better about the awful weather they are having.    Actually, they might even have a big earthquake there in Seattle, too, because they’re under/near a big subduction zone, but, you probably don’t want to mention that….

The End.

 

 

 

 

 

 

 

 

 

 

 

 

In case you missed it….today’s sunrise glory

What kind of cloud am I, up there? Altostratus. Too thick to be Cirrus.   Altostratus in the daytime is duller than staring at dry wall, but, oh my, let the sun shine under it, and there’s no better sunrise, sunset.

What is the colorful bottom of this layer cloud? Light snow falling, strangely believe it.

Looks like a steady diet of these kinds of clouds for a day, anyway.

Also, as the temperature rises above 100 F here in Catland, can thunder be far behind?   Think about it.   Our thundery weather is not that far off now!  Yay!

The End

 

 

 

 

 

 

 

 

 

 

 

 

 

Sunrise and Cirrus splendor; the rarely seen Cirrus castellanus floats by

Gee, three days with a cloud or two over droughty Catalina!   Yay! Here’s yesterday morning’s nice Cirrus uncinus (icy clouds with long trails).

Then, later that morning, the RARELY seen Cirrus castellanus sporting some mammatus (downward protuberances at the bottom) showed up.  (I should note that some of the female atmos sci students at the U of WA preferred to call “mammatus” varieties, “testicularis”.)   I mention this in defference to their preference.

These icy Cirrus clouds, whatever you call them,  are probably the rarest of all Cirrus.  The noticeable cumulus-like shape shown in the second photo is rare up there.   Mainly a steep drop in temperature with increasing height up toward the top of the troposphere (the earth’s blanket of air that contains our clouds (moslty).

Turrets, or cumulus-like shapes in clouds like the “puff” of Cirrus in the middle of the second photo, are also thought to be driven by the release of the latent heat of condensation (in lower, warmer Altocumulus clouds) and latent heat of deposition in ice clouds).  When condensing droplets or as an ice crystal, heat is released to the atmosphere.  This is a HUGE factor in thunderstorms (a lot of heat is released during condensation in updrafts), frequent in cooler,  mid-level clouds such as in Altocumulus castellanus, but,  because there is so little water vapor at Cirrus levels, very unusual way up there.     Yesterday’s cloud were likely forming around -40 C,  at about 33-34,000 feet above the ground.

Below the Ci cas photo is a sounding from the folks at the U of WY.  It hints at a steeping of the lapse rate just above the 250 millibar level (between the 200 and 300 on the left side), and also just below a stable layer  or sideways “v” in the temperature trace up there.

I was quite pumped to see this rare display.   Out of thousands of cloud photos, I have but a dozen or so of Ci cas.   Unfortunately, it seemed, passersby in the Basha’s parking lot when this was about to go overhead, were non-plussed when I pointed out the unusual cloud.  They were mostly polite,  but generally said something like, “Huh?”  It made me wonder what is happening to us if we can’t get excited about a Ci cas?  I started to feel sad.

Later, in the afternoon, when the heavy ice clouds moved in (Altostratus translucidus and opacus) in the late afternoon, you probably were guessing that a good sunset was on tap.  And you were right.   Below an example of that Altostratus, followed by another neat sunset.   Likely to repeat all this today.

Hey, get excited!

 

 

 

 

 

 

 

 

 

 

 

 

 

The End

Catalina cloud drought ends with a whimper Sunday

In case you didn’t see it, here it is, a Cumulus fractus, a real whimper of a cloud. It had appeared in that same spot earlier in the day, before noon on Sunday.  Formed again in the afternoon.  It was pretty exciting, considering we have been absent  clouds for about two weeks it seems.    And this little tyke there, well beyond Charoleau Gap,  did indicate that the humidity here had increased on us as that unusually strong low center moved across the Great Basin and into  Colorado on Sunday.  Perhaps its hard to tell, but that was a “boundary layer” cloud, as any form of Cumulus cloud usually is.   That is, a cloud whose updraft has roots at the ground in this case.

Also, I have a new layer of topsoil in my yard now.   Thank you, 35-50 mph wind gusts on Sunday.   Go here to see the time lapse of a dusty afternoon in Tucson from the U of A.  The Catalinas are barely visible at 17:35 PM LST.

Since this ONE little shred of a cloud popped up in the same spot a couple of times, and also downwind of the Catalina mountains, it may represents a “bounce” in the airflow in the lee of the mountains, possibly a rotor type cloud–no pilot would/should go near this thing on SUCH a windy day!  Extreme turbulence can be observed below this cloud.  If you could see the airflow in a side view, it likely would have appeared like a huge breaking wave with the splash off the ground represented by that cloud.

The second photo is a cross section of another mountain, Mount Shasta in northern California that MIGHT illustrate what was happening on Sunday.  In this shot, a fairly laminar flow is breaking into something akin to a giant ocean wave, and the splash from that “wave” is giving rise to those ragged Cumulus clouds in the LEE of the mountain on the left of the photo.  The wind was blowing strongly from right to left.

So, our one little cloud may have been due to a breaking wave in the lee of the Catalinas, one that would have produced extremely turbulent air.

On Monday, we had just enough  leftovers after a dry cold front went through for this nice sunrise of Altocumulus clouds.  How nice!


Dear commentators…

Still floundering around here doing a blog, and have not been responsive to commentators, haven’t quite done much to improve the presentation here, either, and it needs it.  Many comments I’ve learned since starting up, are not “real” ones, but are advertisements for something.  That said, there ARE  many sincere ones that I have not responded to and I apologize for that rudeness, incivility, to someone who took some time to say something nice.    The “Comments” aspect of a blog was the most fearful part of even starting one;  “what if people actually read this and then said things?”  You might eventually have a career being responsive to those comments, sorting out the real ones from the disingenuous ones, and so forth.

So, I have not yet figured out what to do with comments.   While I will never attain the magnitude of a deeply admired friend’s sometimes controversial climate blog, one that was pummeled with more than 1000 (!) comments in 24 h after a controversial post, nevertheless there is time involved in doing “thoughtful” responses since I don’t write too good and have to go over drafts, a wife, two dogs and a horse to take care of, and am still a bit active professionally.

Mainly the goal of this blog is to pass along some knowledge gained over a lifetime of chasing clouds around, scrutinizing the sky, and in particular, that skill and knowledge gained with the University of Washington’s now defunct Cloud and Aerosol Research Group over about a 30 year period of “soft money” in airborne atudies of clouds.  After all, in a sense, you paid for it via the National Science Foundation, and I thought this blog would be a modest way of paying you back for all those grand years I enjoyed so much.  Below, a couple of shots of one of our more “interesting” maneuvers, gathering aerosol measurements over the surface of the (first, Atlantic, second, Pacific) oceans.  (“Don’t try this at home….”)  Will post a couple more shots a bit later.   The shots were taken between 50 and 150 feet above the surface of the ocean, a height that depended on conditions.  The 3rd shot below was taken from around 150 feet for obvious reasons.

During these many, many scraping-the-ocean’s-surface maneuvers, I made the same comment to the pilot every time:  “Hey, Steve, I just saw a jelly fish….and the jelly fish had a gnat on it.”

The last one?  Had a 16×20 of this shot framed.  At the Seattle gallery where this was done, the person doing it asked,”Oh, did you take this from your boat?”   It was so funny.  It was taken from behind the pilot looking through his window.

Also, and I think its genetic, there is a tendency for goofy (sophomoric?) humor amid the serious commentaries here.

I’ve always tended toward humor as do other members of my family.   I got kicked out of Jr. High classes after puberty due to a lot wisecracks, or actions like riccochetting rubber bands off the ceiling so that they would pile up next to the guy in my class most likely to use them in a more direct manner after he noticed them.  Underlying cause, first principal for humor: there is no greater moment in human relations than creating a laugh or just a smile.

Of course, all of that Jr. High goofiness was REALLY all about girls in those days since I had been a model student, got lots of “A’s” before puberty.   But it was all downhill after that, though a WONDERFUL, EXHILARATING discovery and academic cascade due  to  those marvelously different beings called, “GIRLS!” through Jr. H, HS a I drew attention to myself in unfavorable ways since I was too shy to actually talk to them…  Oops, way off track.

Mainly, thanks for taking time to “comment”!

The end.

 

 

“Smoke gets in your skies”

Remember that great Harold Arlyn song about smog?  He was pretty upset when he wrote it I would imagine.  Btw, the song was covered later in the 1950s by a group called The Platters…

Below we have a shot of some late afternoon pretty, undulating Cirrus or Cirrostratus… (NOT!)

That was a trick question, actually it wasn’t a question, but it was meant to trick you before you saw the exclamatory statement,  “not!”  Perhaps, I was thinking,  you would seriously consider that this WAS a photo of cirrus for just that instant…but then you would be wrong!

But below, for those with the Calibrated Eye, found only in the most discerning of sky watching folk, you will IMMEDIATELY recognize that those waves, undulations in the sky above the tiny Cumulus fractus cloud at the right, is a smoke layer.  Most likely 15,000 to 20,000  feet above the ground, that is, its also well below the normal Cirrus cloud level.  This is, at present an “eyeball” estimate by yours truly.   How can I find out the actual height?  Maybe in the TUS rawinsonde balloon data.   Smoke layers like this are often made visible by a moist layer because the smoke particles fatten up a bit and are made visible because they have gotten that bit larger and scatter more sunlight.  So, this shot was taken near the time of the balloon ascent, and so I will now look and see if there was a bit of humidity around 20,000 feet above Sea Level (balloon data are reported in heights above sea level,  not above ground level.)  Farther below is the Tucson sounding from our friends at the University of Wyoming, which I had not yet looked at whilst (British spelling) writing the above.

As you can see, while there is a “pinching in” of the temperature and dewpoint traces representing the height of the Cumulus fractus moist layer, there really is nothing but a slight moistening (where the lines pinch in a bit) above that lower moist layer.  So, it would appear that my hypothesis of a moisture layer enhancing the smoke layer should be rejected.  But, as a scientist, I don’t care that I am wrong, because it is WRONG to care about whether you are WRONG as a scientist because we are detached from our hypotheses and only seek truth.  Hon, could you get me a new pen since I just smashed this point on this one?  Thanks.

BTW, if you were on a flight descending through this smoke layer, it would have appeared as though an ugly, thin black line of haze, because, after all, smoke is mostly hydrocarbons which are dark chains of molecules.

So why is it white here, when the sun is behind it?  This is due to “forward scattering” of the wavelengths of sunlight, interfered with by those molecules of smoke, which are, in a sense dispersed.  If you had looked to the opposite direction, to the east, you would not even have seen this layer.  The tiny droplets in the Cumulus fractus cloud are really scattering the light around its edges where droplets are likely smaller than 10 microns in size, though at that size,  about ten to a hundred times larger than the smoke particles.

The waves in the smoke illustrate the virtually ominipresence of  waves in the atmosphere.  We just don’t see them unless there is a smoke or cloud layer.

The End.

Not really, since I will, a bit later, see if I can post a trajectory that will show where this layer came from.

 

Sometime later…..

The last figure shows air trajectories for 72 hours at three different levels above ground level and each of the end points are at Tucson AP.  Its clear from these trajectories that this “long range” transport haze layer shown in the first photo came out of the Pacific;  it was not a part of any regional fires.  Haze layers like this have often been observed to come all the way across the Pacific or even from Alaksa in the spring and early summer because the storms in the Pacific are weaker, and can’t wash the smog out.  With the jet stream  still very strong at levels of 10-30 kft across the Pacific at this time of year,  these layers can then make it across pretty much intact.

De-constructing a sprinkle, its THAT dry here…

and that’s what we’re down to.

Today’s topic will be a chapter in the strangely believe it book.  This is about literally about three or four drops at most that hit me at 5:18 PM LST while outside photographing clouds (of course!).   I really didn’t think they  were drops from clouds, I could not see a darn thing that could have done this overhead or downwind, I mean zilch, nada, nil zero, in my esteemed estimation.  I cast them off as something due to a misuse of water by my neighbor.  Definitely, it had to be some pseudo-sprinkle.   Just to be sure, I looked on the top of an iron fence, and there were exactly two drops.  Wow, I thought, could drops really have fallen out of the sky with virtually no cloud???  And more technically, no indication whatsoever of ice in those small Cumulus?  One more check, the dusty car.    It was dumbfounded to see that there was a smattering of small drops there as well!  How could this be?  It was the Twilight Zone for me.

Here is the sky about 10 minutes before (1), one minute before (2) five minutes after (3), and (4) comprises an “explanation”; extremely thin veils of ice crystals can clearly (he sez) be seen below the tiny cumulus clouds.  Perhaps there were just too few ice crystals in those approaching clouds, and those downwind to see any frizzy bottoms due to virga in #3.  I sure couldn’t see it, nor really did I see any ice elsewhere except far to the northwest to north later in the afternoon.

So how cold was it at cloud top?   If you’re really into clouds and stuff, you’ll want to know, of course.

Well, there was a sounding released around 3:30 PM or so in the afternoon for the 0000 Z (Greenwich) time sounding from Tucson.  The tops it indicated were but -10 C.  I will now purport that that temperature is incorrect for the clouds that passed over me and are those tiny Cumulus shown in #4.  Can’t happen with -10 C tops on THIS kind of day.  So I reject that sounding as applicable to MY clouds!  (Hmmm, nice RW- right now at 5:42 AM, yay, might even darken the pavement!)  So what is the best explanation for ice in small clouds?  Probably the air got slightly colder after the sounding was released, but that probably would not account for too much change, but something in the right direction of colder tops than -10 C.  I would say that more important was the stunning drop in temperature aloft as you go north from Tucson being the best explanatory “culprit”.  That is, it was significantly colder of us here in Catalina that it was where that sounding balloon went up.   Being colder aloft would allow the tops to be a bit higher and colder, as well as being cooler just because they were to the north of the sounding.  Flummoxed by this dizzying explanation?  I hope not.  In sum, those kinds of small clouds that produce ice were probably colder at top than about -12 C, and so we’re not talking a lot.

Summary:  Colder to the north, cloud tops were a bit higher, too.  Result, ICE (required for rain nearly always in AZ)!

Just recorded 0.o1 inches here at 5:52 AM!  Yes, Virginia, it CAN rain in SE Arizona!

Now about dust….  Dust has been implicated as helping clouds to rain, particularly in desert environments (sweet!  What an amazing thing that is, the desert soil having particles that help the clouds overhead to precipitate.  Unbelievable.

There is something to that.  In the olden days of the 1970s during the Colorado River Basin Pilot Project, a huge randomized cloud seeding experiment, the highest values of ice nuclei measured on the ground, anyway, was in a dust storm!  Also, in the 1990s,  it was hypostulated that dust from regions upwind of Israel helped clouds to rain on the southern margins of storms where dust was more likely to be encountered.  Finally, during a field project in Saudi Arabia a few years ago, I also experienced an effect of a large particle dust episode on Stratocumulus clouds first hand.  Surprisingly shallow Sc clouds contained drizzle drops and later, ice at high cloud top temperatures, higher than -10 C.  The characteristic of these dust particles, apparently, was to produce a broad droplet spectrum below the freezing level  (one that extends the droplet sizes past 30 um in diameter) and that in turn, accelerate the formation of ice and snow, which melts into rain.  Also, it may be, too, that the dust particles are active as ice nuclei at high temperatures, science speak for triggering the formation of ice at temperatures warmer than about -12 C.

The point of this is that it is POSSIBLE that dust contributed yesterday to ice in shallow clouds, too.

The end