Category Archives: Aircraft Produced Ice Particles

Models warming up to rain; some cloud shots from yesterday

Been kind of sitting around waiting for the billions/trillions of numerical model calculations to get it “right”, that is, to come back with some decent rain SOMEWHERE in Arizona after some pretty sad  dry model results over the past couple of days.

Today,  the great USA WRF-GFS model (rendered by IPS Meteostar) finally got it “right” by showing rain over Arizona on at least three days during the next 15 when it examined global data from this morning balloon, satellite, surface, aircraft, personal weather stations, rumors, TEEVEE weather presenters’ data, etc.   Here are the days on which rain is shown in our great state, a state that ranks 21st in objective measures of subjective happiness by US State.  The first rain is just this Sunday afternoon and evening, the 15th.  Be ready.   This is from the cutoff that got lost off the coast of Baja, one that was a week ago the models foretold that it was supposed to be over Catalina today!  Unbelievable.  It was only off by a 1000 miles.

The second AZ rain day is Saturday night into Sunday, the 21st-22nd.  This rain is only supposed to stay north of about Phoenix.  That’s OK.  That’s followed by a much heavier burst of precip on the night of the 23-24th, again mostly north of us (3rd panel).  That’s OK#2.  We benefit when the rain and snow falls in the north, too.

Lots to look forward to!

BTW, when that Pac jet slams the West Coast from the central Pacific, starting next Tuesday afternoon, it will cause a lot of excitement for weatherfolk and plain folk as floods develop over the following few days in northern California and Oregon.  In some places in northern California it has been as dry as the Great Drought of 1976-77, which was dang dry along the whole Pac coast.  They’ll soon be “exulting-complaining” about all the rain filling up the reservoirs and washing things away, respectively.  Watch your local newspapers.

 Yesterday’s clouds (see below)

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What a great, if a cool day it was, to watch Altocumulus and Altostratus pass by. There were a number of places where it looked like an aircraft may have created some virga in supercooled Altocumulus clouds, but lots of natural mammatus type virga, too. You can see the whole day go by from the U of A campus time lapse camera, pointed at the Catalina Mountains, here.  That small hole in  the middle shot was likely caused by an aircraft, the ice from that passage, long gone.  And, of course, there was the superb sunset!  How nice it is to be here.

While waiting for a “better” numerical model output….

As we say, “if you don’t like the model run now, wait 6 h and get a new one with different results.”

Last night’s model run based on global data taken at 5 PM Arizona time, was truly mediocre in rain in Arizona in the week to two weeks ahead.  Sure, great storms bash northern California, where they need rain desperately this year, and Washington and Oregon as well, ones that are likely to make the news, the jet stream was again retracted to the north in that run.  Take a look at this, courtesy of IPS Meteostar for Sunday, January 22nd and notice where the reddish area is compared to the output I showed yesterday (below).  The impacting jet stream is now centered over Portland, Oregon, fer Pete’s Sake!  Its outrageous.  No rain is imminent here with a map like that!  We’re on the wrong side of the jet stream as anyone can see.  Just yesterday, we had the kind of output from global observations that showed the Pacific jet stream (JS), this on model calculations from only six hours earlier than the output shown in the first panel.  As you can see, in that slightly earlier run, the JS is shown bursting into California at almost the exact same time on January 22nd instead of into Oregon.  That second panel was loaded with rainy portent for Arizona (see last panel)!   So, its worth checking into IPS Meteostar, a weather provider I favor for their nice imageries, later today to see what the 5 AM AZ Time global obs say.

Why do these fluctuations occur that prevent confidence in weather predictions more than a few days out?  Well, we have a reason:  “bad balloon.”  (Or “missing balloon.”)

While small changes in initial conditions in themselves can cause vast changes in model outputs many days ahead, sometimes these problems are caused by errors in measurements and probably more often, missing measurements in the global network.   The models then have to guess what is happening in the missing data regions, usually with the help of satellite measurements, and/or use the prior model run’s prediction of what was supposed to be in the missing region.

I am getting the impression that the quality of the 00 Z runs are not as high in reliability 1-2 weeks in advance as those at 12 Z.

In the meantime, while waiting for a new more better model run, a word about today’s clouds…

Right now (8:44 AM AST) we have an overcast layer of Altocumulus (Ac) with patches of Altostratus (As) clouds. The former are mostly composed of droplets while the latter are ice clouds. The TUS sounding indicates that the Ac layer is based at -20 C (-4 F). Those Ac clouds are ultraripe for aircraft produced ice, and right this minute, I would say that much of the virga around is due to aircraft on those “supercooled” clouds. This is particularly evident if you see straight lines of virga, or a hole with ice in it. Here’s a line of virga (those downward hanging protuberances called “mammatus”, to the SW of Catalina right now that looks suspiciously like it may have been produced by the passage of an aircraft through some Ac.  That passage would cause tremendous numbers of ice crystals to form, and then fall out as fine snow we call virga.

“(the reviewers)… are still unconvinced by these controversial claims.” A science story.

Alternate titles, choose one or all:

 1) The story of APIPs (Aircraft-Produced Ice Particles)

 2) They said it couldn’t be done, but they did it anyway

 3) ‘An embarrassment for the airborne research community’–Dr. John Hallett, 2008

OK, “baby I’m bored” with the lack of clouds and precip,  and so I thought I would share my boredom with this long tome on aircraft effects on clouds.  Why not bore other people if you’re bored?  I’ve thrown in some alternate titles above to peak and pique your interest.  Speaking of “thrown”,  Mr. Cloud-maven person was also thrown off his big (I mean huge1),  young horse lately; “JohnT”, as he is named, doesn’t like people to sit on top of him sometimes.  Not easy to sit at a computer these days, hence the lack of “acitvity.”

OK, on to the story of APIPs.  The title quote was written in 1982 by the Chief Editor of the American Meteorological Society’s, J. of Climate and Applied Meteorology (JCAM) summing up the opinions of the three reviewers at the bottom of a second rejection notice of a manuscript, one that had been fluffed up with more evidence of APIPs.   However, the Editor allowed us (me and Peter Hobbs, director of the Cloud and Aerosol Research Group at the University of Washington) another crack at it, and by the THIRD submission (requiring a bit of chutzpah),  a colleague and me had found photographic evidence of aircraft having produced icy canals in supercooled clouds, and that visual evidence really pushed our third manuscript, now as big as JohnT, over the top in getting accepted and  published.

The phenomenon came up again last summer in a Wall Street Journal article, one in which Mr. Cloud-maven person was asked his opinion.  This phenomenon (APIPs) is attracting more attention these days, so I thought I would pass this background story along.  I hope will encourage authors with rejected manuscripts, which I myself have quite a few.   You might have something really good.

Yes, that’s right, lucky Mr. Cloud-maven person was involved in this interesting chapter of science that happened way back in the early 1980s when he was part of the flight crew in the University of Washington’s Cloud and Aerosol Research Group (CARG).  Occasionally, and mostly in studies of ice development in Cumulus clouds, I got to direct the University of Washington’s first research aircraft, a 1939 manufactured, Douglas B-23, into Cumulus and small Cumulonimbus clouds.  It was heaven for me, a storm chaser type person, having done that here in AZ way back in the mid-1960s chasing summer thunderstorms all over the State with my camera and rain gauge.

We had a viewing dome on the top of the fuselage of that B-23 and I sat in a swivel chair, head protruding into the “bubble.”   I was kiddingly referred to as the “bubblehead.”  I think they were kidding, anyway…  Those who know me will understand that title.   Sitting there with head in the bubble, allowed me to see EXACTLY where we exited a cloud and could direct the pilot to EXACTLY that same cloud blob we had just exited.  The pilot was fond of turning the plane sidewise for this return so that one wing was pointed straight down in the turns and we often got back in within 90 s to two minutes.  It was an exciting as well as sickening experience.

We did that because we wanted to see how that element of the cloud had changed with time.  Did ice form?  Did the drops get bigger or smaller?

This viewing dome gave us a huge advantage over other research aircraft doing this kind of research.  Below, that B-23 aircraft sitting on the tarmac at Boeing Field, Seattle2.  The second photo is a view from the “bubble” located toward the rear of the fuselage.  Nice!  I was so lucky!

One day, while looking over our Brush strip charts from the flights, I noticed some odd spikes in the ice crystal detector we had. Also, since we were one of the first groups to get a probe that produced shadows of the particles in the clouds as we flew in them, I was able to see that the particles producing those spikes were oddly similar sized, as though they had formed simultaneously, something not seen so much in natural clouds. Pretty soon it became apparent that these spikes and odd particles ONLY appeared after we had gone through the same cloud for the second or third time.

I remember walking into Professor Peter Hobbs grand office with a strip chart with those ice spikes and saying, “I think our aircraft did this.”

He was unfazed; did not have a particular reaction.  Peter Hobbs was always open to new thoughts, and that helped allow me to go forward with a further investigation even if it meant some of our past data and publications might conceivably be compromised, ones however, I was not involved with as a fairly new (5-years in) employee at the U of WA.  No vested interests here!

After awhile, after aircraft plots showed that the spikes were within tens to a couple of hundred yards (meters) of where we had been before in a Cumulus cloud, a very short paper was written up on it and submitted to JCAM in late 1981.  It was quickly rejected.

Ours was a highly controversial finding due to both the high concentrations of ice that we found (hundreds  to over a 1,000 per liter) but most of all due to the temperatures at which we were reporting this effect, -8 to -12 C.   Our plane was,  in essence,  seeding these clouds with ice crystals, changing their structure.  Since the volume affected was initially quite small, it was likely that only having the viewing dome allowed us to find them on the second and third penetrations of the clouds.

This inadvertent aircraft effect had even been looked for by our aircraft group leader, Dr. Prof. Lawrence F. Radke before I had arrived and after the University of Washington acquired the B-23.  He didn’t find’em though.  Larry was also aware that an aircraft COULD do this in those early days with the B-23.

So, when I found them and a paper began taking shape, the skeptical Larry Radke called them,  “Art-PIPs.”  It was so funny.

Later, with the skeptical Larry at the helm, we got some money from the NSF to try to produce them in various clouds, and sure enough, we did.  It was amazing finding those crystals in those test flights since even I couldn’t be absolutely positive sure that this was real.  Why hadn’t this phenomenon been reported decades ago?   That, too, was part of our problem:  why you, why now?  And why hadn’t I seen the holes and canals of ice produced by aircraft as a cloud photographer for decades even by then?

Some ground observers had seen trails and holes in “supercooled” clouds like Altocumulus.   Those holes and canals were occasionally reported over the decades (!), but not in the technical journals.  A couple of really lucky observers had even seen the type of aircraft that had caused them.  But the airborone research community, ignored or did not know about these reports, ones that appeared in non-technical weather magazines like Weatherwise, Weather, and Meteorological Magazine (the latter two in England).

Furthermore temperature data were nearly always absent in these visual reports.  So, it could be reasoned they had occurred at very low temperatures, below -25 C or -30 C.  Clouds that cold, but still consisting of only or mostly of liquid droplets do occur, the ones in which an aircraft could leave an “ice canal” or a “hole” with ice in the center, falling slowly out.

If we had been reporting our finding at cloud temperatures of -25 to -30 C, maybe we’d have got into the journal on the first try and reviewers would have yawned.  But at -8 to -10 C cloud temperatures?  No way!


Research aircraft had been going back and sampling the same cloud, usually a Cumulus one,  for a couple of decades by the time of our report.   Furthermore, those aircraft re-penetrations were almost always in the same temperature domain that we were reporting this effect, to about -5 t0 about -15C.  And one of the main findings in those early days of aircraft sampling was that nature was producing far more ice in clouds than could be accounted for in measurements of ice nuclei, particles on which ice can form.  Concentrations of ice nuclei were largely determined from small cloud chamber measurements made on the ground.

These early cases of high ice concentrations in clouds with tops that were not very far below freezing (greater than -15 C) were called cases of “ice multiplication” or “ice enhancement.”   No one understood how such ice developed and many theories were put forward initially in the 1960s.  The issue was largely explained by the “Hallett-Mossop riming and splintering mechanism”, a mechanism discovered in the mid-1970s and today is still believed to be the primary reason for high concentrations of ice crystals in clouds with tops warmer than about -15 C.  Oh, yeah, ice multiplication is real and NOT due to aircraft penetrations!

But our paper on APIPs, if true and published,  would cause researchers to have to go back and look at their research data (even us!) and investigate whether their own aircraft had contaminated their published studies with artifact ice crystals.  An entire body of airborne literature would come under question.  This was not a pleasant thought for anyone who had  conducted such studies.

Why would you go back and sample the same cloud?

To see how it changed with time.   How many ice crystals formed as time went by?  Where, and when?  These were techniques used in trying to get to the bottom of the “ice multiplication” phenomenon.  In fact, the Chief Editor of JCAM himself was involved with numerous aircraft that sampled clouds in a huge summer Cumulus cloud study program in Montana in those days (called “CCOPE”-Cooperative Convective Precipitation Experiment)  That study, like so many other airborne studies, was to determine how ice onsets in clouds, how high the concentrations of natural crystals were in clouds with various cloud top temperatures, and the potential of cloud seeding to increase rain.

While academic scientists did not particularly welcome these reports and were dubious and largely ignored them (did not change their aircraft sampling strategies), or when they looked could hardly find any APIPs, it was soon evident that purveyors of cloud seeding services were elated!   Our finding suggested to THEM that all that natural ice formation reported in re-penetrated clouds  in research articles over the years might be wrong, and rather due to ice produce by the aircraft!  Maybe those clouds that had been reported with a lot of natural ice, which made them unsuitable for seeding, was because the researcher’s aircraft had produced it, not nature.  Purveyors of seeding would like clouds that are below freezing, about -5 C and colder, with no ice in them.  If the concentrations of natural ice crystals forming in clouds ice get to 10s to 100s per liter,  those clouds are deemed unsuitable for seeding to add more ice.  The crystals might be too small if you add more in those cases, and not fall out.  If surveys of clouds in a region find that they have lots of ice in them, its “no paycheck” for commercial cloud seeding interests. (Usually, cloud surveys aren’t done before commercial programs begin.)

Thus, those who had interests in cloud seeding actually saw our result as a way to discredit findings of high natural ice concentrations in clouds, findings that made them appear unsuitable for seeding.  It was a bogus argument since numerous FIRST penetrations of clouds had encountered high ice particle concentrations, still, they had SOMETHING to hang a hat on.

This was indeed an ironic twist, being supported by the cloud seeding community!

Me, usually with Peter Hobbs as a co-author, had been discrediting various published cloud seeding results in the literature via reanalyses and journal commentaries for several years (e.g., here) when our APIPs finding finally hit the “streets” in 1983.

Given these a a priori possible biases between academia and in the commercial cloud seeding world in detecting APIPs you can imagine where the major “confirmatory” studies of this phenomenon came from. Yep, those associated with cloud seeding programs!  It took 8 years (1991) for our finding to be independently confirmed (the best way) using several types of aircraft in marginally supercooled clouds.   Then pretty much the same workers amplified their findings with another paper in 2003 WOODLEY et al. 2003.  For those of you who don’t know the cloud seeding literature, Woodley and Rosenfeld and Peter and I have had a major clash in the cloud seeding literature (i. e. and big i. e., and bigger still)

We loved it!  They loved it!  Even the great John Hallett got involved and found in lab experiments that the mechanism was the extraoardinary cooling at the prop tips, momentarily down to -40 C, a temperature at which ice forms spontaneously in high concentrations (here).  It had also been suggested that prop aircraft could do this by the late Bernard Vonnegut back in the late 1940s in a less widely distributed report from a General Electric research lab and in the J. Applied Physics.

Today this phenomenon is taken pretty much for granted, and has been more widely detected from time to time in satellite imagery in thin clouds as here.  In thicker clouds, the effects of aircraft go largely undetected.  Recently, in a widely distributed news release that accompanied their formal publication, Heymsfield et al reported a case in Colorado in which aircraft-produced ice effected a snow shower on the ground instead of just being a hole or canal in some thin clouds as we normally see.  They opined that aircraft could actually help delay flights from the airports that they were taking off from or landing at in special conditions.  (That’s what the Wall Street Journal article was about.)

Why was it an “embarrassment” to the airborne research community, as John Hallett (of Hallett-Mossop) asserted?  Because they should have found out about APIPs right from the get go, especially in view of the occasional lay publications that had photographs of ice canals in supercooled clouds even in the 1940s, ones  that could only have been produced by aircraft.  It turned out to be a major oversight.

Below, a cartoon I did before the paper was accepted making fun of how a researcher, thinking that natural ice multiplication processes were taking place (i.e., the Hallett-Mossop riming splintering mechanism) might overlook all those ice crystals streaming off, in this case, the Husky 1 aircraft.

Below, some photographic evidence of what aircraft can do to supercooled clouds, the last one taken about two weeks ago over the Cat Mountains.

Finally!  The End.










1The 6-year old horse in question is about 15 hands, 1200 lbs, not really a Clydesdale.  I have overemphasized our horse’s size for personal reasons.   You don’t want to be injured getting bucked off a Shetland pony, but rather something HUGE!  It just sounds better.

2That B-23 aircraft, wherever it went, brought a crowd out to see this antique “tail-dragger.”

Grandson of “Frankenstorm” knocking on Heaven’s door (Catalina, Arizona)

Well, I think Catalina, AZ,  being next to the Catalinas, is “Heaven’s door”.   I think, too, to have a second consecutive thought,  that we’ll get more than an inch out of this Big Boy which is rare here in Catalina for a storm in the wintertime.  Not close in areal extent to the original “Frankenstorm” that struck the West Coast in January 2010 with record setting low pressure, but a potent one anyway.   In the January 2010 storm we received 1.41 inches the first day and 1.18 inches the second to “ice” a fabulous wildflower bloom that year.  We sure seem headed to a fabulous bloom season this year, too.

BTW, there has been a lot of rain in droughty Texas.   We are brothers/sisters in drought relief it seems these days.  How nice; adds to the holiday cheer.  Maybe the price of hay will go down..  It seemed interesting to throw something about Texas in there.  Here is a map showing that great TX rain of yesterday from WSI Intellicast1.  These radar-derived amounts precipitation are pretty much spot on–I’ve checked ground gages a number of times.  We should be seeing “green”,  1-2 inches) over much of AZ in the next couple of days, too.  So, the map below is like a preview for AZ.

Speaking of green, look at the “green-for-rain” in AZ in the lower right hand panel of this forecast for this afternoon ending at 5 PM MST.  During the prior 12 h, beginning at 5 AM MST, the entire State of AZ is virtually covered.   I am just beside myself when I see a map like this!  And look how far to the south of Baja California the circulation of the storm extends.  Its gorgeous to see this.   I guess there could be some flooding here and there, and some “snow birds” might complain about the “crummy AZ weather”, but….you can find people who will complain about anything.  See the whole wonderful model sequence of rain and mayhem in AZ here, and in much more detail from the U of A weather department, here.

Look, too, at how excited the National Weather Service, Tucson is!  They must have 50 bulletins out–be sure to keep reading them.  They are really having a lot of “fun” down there, too.

Late breaking storm bulletin:  We have sprinkles in the area (0425 LST).  Check this radar-cloud map out from IPS Meteostar.  What a great day this is going to be!  Enjoy.   Good chance we’ll see water in the CDO and Sutherland Washes, and maybe some snow mixed in with the rain as the storm closes out Tuesday evening now.

But is this storm the end of our “fun” weather?  Oh, no, my friend.  Another cut off low develops in our area after speeding down as a trough out of the NW in five days.   Another round of significant rain is likely, though not as much as this one.

Some cloud notes from yesterday, including some chat about the unusual streaks.

In that warm afternoon yesterday, it was so great seeing sheets of Cirrus and Altostratus (ice clouds, Altostratus with heavy shading) massing on the horizon, knowing that this time it was NOT just going to be a sky decoration for a nice sunset, but were clouds filled with stormy portent. You probably noticed the lack of sunset color due to the extensive coverage of those clouds upwind. No break allowed the sun to under light them, a sign of extensive clouds upwind to the southwest.

Also, unless you were blind you saw some unusual events in the thin Altocumulus (translucidus) layer yesterday: ice canals and splotches of ice produced by aircraft that flew in them. When so many happen as did yesterday mid-day, its a good bet those Altocumulus clouds, though comprised of liquid droplets, are terribly cold. While the TUS morning sounding did not pick up this mid-day layer, one can be confident that it was likely colder than -20 C or -4 F.

What you also saw was examples of how the presence of ice within a droplet cloud, causes the droplets to evaporate, and the ice crystals to grow and fallout, something that happens on our rain days. However, because there were so many ice cyrstals produced by these aircraft (almost certainly all jets) they compete for the tiny amount of water available at -20 C and form small crystals with little fall velocity.

So the trails of precipitation are very fine and don’t go very far. Here are some examples of that rare phenomenon, rare because for us to see it, takes a thin, cold water droplet cloud, and it has to be high enough so that aircraft are frequently penetrating it. One wonders why, in some of these cases, the trails yesterday were so long with an aircraft probably could have climbed or descended a couple of hundred feet to avoid flying in a light icing producing cloud (the Altocumulus layer composed of supercooled droplets)?  Note “ice optics” in ice canal in the first photo, a weak sun dog so I didn’t just make it up that the canal was ice.  I you wanna know more about this phenomenon, go here and/or here.

More about holes-in-clouds while we’re waiting for the AZ rain in a few days

There have been a coupla comments on that aircraft effect in clouds blog of a coupla weeks ago and so I thought I would follow up with this sequence from the Atmos Sci Building rooftop at the University of Washington where I spent most of my time instead of at my desk.1

Here is a rarely photographed sequence of the effect of an aircraft on a supercooled cloud.  The first photo, right after a contrail-like feature was seen in these Altocumulus clouds.

Look at what seems to be a dark contrail-like line in the middel of the photo. The Altocumulus (perlucidus) cloud layer, mostly comprised of supercooled liquid drops, is probably around -20 C, though I did not get a PIREP on this day for some reason.

In the minutes after this first photo, the aircraft trail seems to disappear as it widens and the shadow lessens.  This stage is not shown because I didn’t realize what was going to happen until minutes later.   This second stage is almost impossible to pick up visually because there are no ice trails yet, nor is the cloud opening up at this time.  This “invisible” stage might last 5 minutes before you see the hair-like signs of a fallout of ice crystals.

This second photo is about ten minutes after the line in the first photo. Now it is clear that ice has formed, the crystals are growing and falling out as "virga", and a clearing is starting to open up.

Ice grows rapidly in the presence  of the supercooled drops.  Ice represents something of a low pressure center in the middle of all those droplets and that attracts the vapor from them, causing them to evaporate.  That vapor deposits as ice on the newly present ice “germs”/crystals created by the aircraft.   Since the drops are disappearing, before long, you get a hole or ice canal in the cloud where the droplet cloud used to be.

In this third photo, there is no longer any doubt about what's is going on. The hole is there, and its only a question of how much larger it will get.

The ice crystals shown above are clearly falling out (ever-so gradually because they are so small still, perhaps a few hundred microns in width).   Becasue they are so small, they usually evaporate well before any precip reaches the ground.  However, recently it has been shown that in deeper clouds and more moist conditions, that an aircraft can actually produce a bit of rain/snow at the ground due to this effect.

Here is last photo I took that day.

The ice crystal induced hole in the Altocumulus layer has gotten closer to exiting the liquid cloud (has moved to the edge of it) as well as expanding some.  This suggests that the ice cloud was moving faster than the droplet cloud, something that happens when waves in the atmosphere are producing the droplet cloud.   It was also getting closer to the observer, however.

Sometimes, if the cloud layer is lifting enough, the original Altocumulus clouds will gradually fill back in because all of the ice has settled below the liquid cloud layer.

For history buffs, holes in clouds with ice in the center, or ice canals were seen in the 1930 and 1940s, but as you can see, unless the observer saw the original trail (which they usually didn’t) no one knew what caused them.   Eventually an ice canal was was photographed in 1946 that was so convoluted it was realized that ONLY an aircraft could have done it.

Furthermore, that report in 1946 preceded the discovery of modern cloud seeding with dry ice by Vincent Schaefer in 1947 who performed his most convincing, and could be seen as ironic, demonstration of seeding with a similar convoluted ice canal as was seen in 1946 in a supercooled Altocumulus cloud layer  Its interesting in retrospect, as so many things are, that Schaefer did not have to drop dry ice on his clouds that day in 1947 in which he made history, but rather only had to fly his prop aircraft through them and likely would have gotten the same effect!

BTW, there is a lot of new interest in this topic, a new article recently appearing in Science mag.

I mention this cloud seeding benchmark since these aircraft events represent inadvertent cloud seeding, and in a sense they demonstrate that you CAN get something in the way of precip to fall out of a previously non-precipitating or barely precipitating cloud by seeding.  When clouds are already naturally precipitating, what happens when you do cloud seeding is subject to question; the science domain in this murky world is highly polarized.

The “Story of APIPs”–Aircraft-produced Ice Particles)  is told (in the usual “style” you will often find here) in the gigantic powerpoint “show” on this website under Sci Talks toward the middle of the show, around slide #472 (hahaha).

This ppt “show”, BTW,  is WAY overdone, but, what the HECK!  Why tell only “the whole 9 yards” when you can tell 12 or 14?


1Hahaha, sort of.   Sometimes, looking at those several thousand film shots from the rooftop of the Atmos Sci Building, I do wonder about that.  But then again, since I used 1/100 of a second exposures with my film cameras, these photos would only PROVE that I had been on the roof, maybe 30 seconds in 30 years there at the UW.

Feeling better now.

What’s Up with This?

Got pretty mad yesterday when I saw this overhead in some Altocumulus perlucidus clouds.  You’ll have to hold your monitor or Ipad, or cell phone, or whatever, over your head to see it EXACTLY the way I saw this because it WAS overhead;  straight up.  (Actually, doing 3 sets of 12 might be good for you.)  Also, click on images to get the full view.

As you can see, the white strip below in these clouds is a contrail caused by an aircraft, but a special one that occurs in “supercooled” clouds.   Supercooled clouds are clouds that are composed of drops, yep, they’re still liquid, even though the temperature is FAR below freezing.  Here, the clouds were likely colder than -20 C (-4 F) and yet there is no ice forming in them!  (You don’t see trails of snow coming out, do you?  No.)  Run of the mill contrails occur at cirrus levels at temperatures below about -35 C  (-31 F).

Note that except for being much whiter than the surrounding cloud, the elements are exactly the same size and texture as those around it.  That is going to change, because this white strip is composed of “horrendous” concentrations (probably thousands per liter) of ice!   You can only know this by what happens later.

In the next shot below, is an example of what happens later, trails of tiny snow crystals fall out leaving a hole in the droplet cloud, so called, “hole punch” clouds, a form of inadvertent cloud seeding by aircraft.  Note the delicate strands of ice crystals falling out of this cloud from the hole, so pretty because they are so delicate looking.  Note, too, I am one of the “trailing authors” of the journal article above, like one of those itty bitty ice crystals in the second photo which are almost evaporated at the bottom of those fine strands.

So why be upset?

Rather than looking forward to good things in the coming year, this happenstance yesterday reminded me of all the trouble we had in the early 1980s trying to get our paper published on this phenomenon; namely, that an aircraft could produce tremendous amounts of ice when flying through supercooled clouds, inadvertently seeding them.

In the SECOND rejection of our manuscript (with Pete Hobbs), the Editors words still burn; “(the reviewers) are still unconvinced by these controversial claims.”

We had to do a LOT of extra work on this to convince those reviewers.  The third version was more convincing, I guess, for intransigent reviewers, and got published.  In fact, one of the great scientists of our time as far as clouds and ice crystals go, John Hallett (yes, the same one as in the “Hallett-Mossop” ice splintering process),  speaking at the Peter Hobbs Symposium Day in 2008 called this episode, “an embarrassment for the airborne research community.”  “Hey”, he wasn’t referring to our paper!

He was referring to the fact that such a phenemenon had been overlooked and not accounted for in research studies of clouds by aircraft.  Actually ground observers had been reporting this kind of thing (ice canals and hole punch clouds) since, if you can believe it, the 1930s!

BTW, this hole is not the one from the first shot; I got distracted and forgot to follow it until it was disappearing over the horizon.

BTW#2,, this shows what happens when you introduce ice into a supercooled cloud; “stuff” falls out.  Proves cloud seeding works, though for sure in limited venues like these (non-precipitating, supercooled clouds).

BTW#3:  The second photo is a nice example of the difference between supercooled clouds composed of tiny drops (probably less than 20 microns in diameter), and cirrus-ee ice clouds, composed of much larger crystals (here probably 100 or 300 or so microns in maximum size) that tend to settle with time. (Hence, those strands in most cirrus clouds.

BTW#4:  Today’s title is cribbed off the world’s most viewed climate website, “What’s Up With That?”  Mr. Watts, host of the site, has made significant contributions to our climate network by pointing out flaws, but has no “credentials” beyond having been a TEEVEE meteorologist.  He is excoriated on this point alone by “credentialists”, as I myself was when I first began to reanalyze other folks’ cloud seeding experiments such as this one.

BTW#5, a movie about credentialism is now out, called,  “The King’s Speech.”  I highly recommend it.   In this documentary, which I just saw yesterday, it will be seen that the credentialists in the King’s Court were royally put out by the help the King got by his uncredentialed therapist.