Saudi Arabia – Cloud-maven

Weather “stagecoach” full of storm presents set to arrive on Friday

Don’t really need me anymore. Everyone’s on top of this ” incoming” now, set to begin in the area overnight on Thursday, the one you’ve been reading about here since maybe last October I think. So, feeling sad today, also because it looks like its going to be a bit too warm for snow, which I think I mentioned about a dozen times. Maybe I will take it out on you by boring you with a science story, one about ice in clouds…but one featuring such stalwarts as Sir Basil Mason, Stan Mossop, John Hallett, Pete Hobbs, Alexei Korolev, and others. Interested now?

But first, a few nice cloud shots from yesterday so you don’t get too mad at me for boring you first:

2:07 PM. CIrrostratus fibratus (has detail, not just an amorphous veil).

4:21 PM. Cirrus spissatus patches and dog, Zuma (named after the acclaimed dramatic series, Baywatch, which took place at Zuma Beach, also where the author, whilst not storm chasing spent a LOT of time. — 4:21 PM. Two dense patches of Cirrus spissatus patches and dog, Zuma (named after the acclaimed dramatic series, Baywatch, which took place at Zuma Beach; also where the author, whilst not storm chasing, spent a LOT of time.

5:22 PM. Cross section of a Cirrus uncinus (hooked at the top). This shows how the ice crystals forming at the top first get heavy enough to fall out, but if encountering drier air, start to evaporate, slow in fallspeed, and as in this case, form a flat layer of tiny crystals at the bottom of the head of Cirrus uncinus. Likely a little moist again at that bottom location so the tiny guys don't away very fast. — 5:22 PM. Cross section of a Cirrus uncinus (hooked at the top). This shows how the ice crystals forming at the top first get heavy enough to fall out, but if encountering drier air, start to evaporate, slow in fallspeed, and as in this case, form a flat layer of tiny crystals at the bottom of the head of Cirrus uncinus. Likely a little moist again at that bottom location so the tiny guys don’t away very fast.

5:29 PM. Sunset in Cirrus (spissatus and others).

Cloud ice science story

(drink some coffee, maybe take an extra swig of an “energy drink” if venturing forward)

Kind of takes the fun out of it when other people are saying what you want to say by yourself, lilke today’s forecast for Friday’s storm. Kind of like being second when you publish “new” results behind other researchers who “got in” a little a head of you (like Korolev et al.-with Hallett!) did in 2004 reporting the FIRST image of a shattered frozen drop they said.

Drop shattering during freezing; what about it?

It was thought not to happen in natural clouds after that embarrassing episode back in the 1960s when the Great Knighted, Sir B. J. Mason¹ and his student, Swinbank (1960), reported drops exploded with they froze. Liquid centers tried to get out of the ice shell as the drop froze from outside in, as you would expect, but then blew up when the freezing water expanded inside the shell. Looked pretty good.

There was only one thing wrong, their findings weren’t valid for real clouds.

They put too much CO2 in their cloud chamber (that’s right, the very SAME stuff that’s supposed to make the earth warmer and warmer year after year but has been sitting around lately, about 15 years actually, not doing anything) and that CO2 in the experiments turned out to make the outer ice shell real weak, and also the CO2 came out of solution in the water in the liquid center to make matters worse by expressing gas through the shell. I wonder how many people have done that?

This was found out by researchers in my very own group before I got there, Jim Dye and Peter Hobbs, a few years later. When real air was used, the drops didn’t explode. So, down that hypothesis went that exploding drops caused a lot of ice to form in natural clouds.

End of story? Nope.

Later, Hobbs with grad student, Abdul Alkezweeny, repeated the experiments with freezing drops, but this time instead them just sitting there, had them rotate as they froze and they DID shatter some, but not a lot! This was back in 1968.

But no one was reporting images of shattered drops.

In those days, there was a HUGE amount of unexplained ice in clouds. Cloud chambers on the ground and in aircraft, found that little ice formed until the air IN THE CHAMBER was at least as cold as -20 C (-4 F), but instrumented aircraft repeatedly found tremendous amounts of ice in clouds that had never been colder than -10 C (14 F). Hence, an enigma.

But the explanation that a few drops exploded, sending out thousands of ice shards never gained any ground because there was never any observational evidence that it happened. Instead, an Australian researcher, originally from South Africa, Stanly C. Mossop, with John Hallett, discovered in 1974 that a bar moving through a cloud chamber between -2.5 C and -8 C, caused ice splinters to eject from SOME of the little drops hitting the bar and freezing on it. But the drops had to be at least 24 microns in diameter, fairly large for cloud droplets, or nothing happened. Also, if they moved the bar too fast or too slow, nothing happened. So, there were a lot of criteria involved in this process, temperature range, drop sizes, speed.

So, the Hallett-Mossop riming-splintering hypothesis was born. They assumed the bar, moving at the fall speeds of soft hail, showed what soft hail did inside clouds: multiply ice content!

It was an exciting time to see that the mystery of all that ice in clouds at higher temperatures was finally explained, not needing, shattered drops or anything else.

But there were some problems. In the early days, it was thought that this process, to raise the ice concentrations in clouds much, would take as long as 1-2 hours because it was a “cascade” process. The few first splinters had to grow to sizes there they fell fast enough to bump into drops and cause ice splinters to eject. Well, that wasn’t right. Natural clouds formed ice MUCH faster than that, as you here in Arizona know so well.

The experiments continued and it was found that shattering helped this process (assuming it occured, but even more important was the freezing of drizzle and raindrops. When those froze, they became instant rimers, splintering objects, and so the time for a cloud, but one having drizzle and raindrops in it, and in the right temperature zone, just between -2.5 and -8 C, was cut down to minutes, something like 10-20, to get ice concentrations from about 1 per cubic meter, to tens of thousands per cubic meter, a real rain cloud.

Except for a single image of a drop half by a researcher using a cloud camera with a glider in the 1970s, no one had reported a shattered drop. Then along come Korolev et al. (with the great Hallett!) in 2004 reporting shattered drop images in a Canadian frontal band using an advanced cloud camera. They wrote that it was the FIRST images ever reported of shattered drops. Rangno and Hobbs (2005) also reported images of shattered drops in clouds around the Marshall Islands, thinking at the time that they were going to be first in line, and then discovered the Korolev et al. report. It was a sad day to find that reference, as a researcher that was thinking about the glorious days ahead, the keynote addresses to important conferences, that would result from being first in line with something and then other people would always have to reference you.

As Ecclesiastes wrote, their is hardly anything new under the sun if you’re slow going about it.

Published another paper on shattered drops back in ’08. But, found they didn’t SEEM to be making a big contribution to the ice content in clouds, less than 10%. You can go here to see that I didn’t make that part up. That was kind of sad finding, too. You want what you find to be HUGE, and it wasn’t so huge as I hoped.

So, riming and splintering remains our best, most accepted explanation for the great amounts of ice in clouds that aren’t so cold, though the author and Hobbs, have mostly found it wasn’t powerful enough to account for the speed of ice development. Only the author’s friends, Stith et al (2004), have reported a lot of ice that couldn’t be explained by the riming-splintering mechanism as have R&H over the years.

But it would be so great if others confirmed the Stith et al findings.

The End for now.

———————-

1Wiki doesn’t do a very good job, and doesn’t even list his outstanding updated, Physics of Clouds text published in 1972, the “bible” of cloud physics in those days! Unbelievable.

²Riming: Think of what happens to an airframe in a liquid drop cloud at below freezing temperatures. HELL, here’s a photo by the author from the author-occupied Lear Jet 35 flying in supercooled clouds over Saudi Arabia, 2006, The weapon-looking things under the wings image precipitation particles like raindrops and snowflakes using laser beams with light sensitive diodes at the other end, one that when shadowed, give you a two dimensional image of what went through the laser beam.

ann DSCN1223 rime icing — 8:01 AM, December 16, 2006.

11:02 AM, December 10th, 2006. Had to land at Hail, a small, pretty town north of Riyad to pick up some supplies, ones for the randomized cloud seeding experiment underway. It was interesting that we could carry these boxes labeled "Explosive" to the Lear Jet without any notice. Hmmmm. — 11:02 AM, December 10th, 2006. Had to land at Hail, a small, pretty town north of Riyadh to pick up some supplies, ones for the randomized cloud seeding experiment underway. It was interesting that we could carry these boxes labeled “Explosive” to the Lear Jet without any notice. Hmmmm. They were there because that’s where another NCAR radar was besides the one at Riyadh, and a plane might have to land to continue seeding if it ran out of the seeding flares like the ones inside these boxes.

Yesterday’s drizzle

Some rare drizzle precip¹ fell yesterday. Suggests clouds were pretty “clean”, that is, didn’t have much aerosol loading and the concentrations of droplets in them was low (likely less than 100 cm^-3) Also likely, in view of the recent strong winds, some of the aerosols in those clouds might have been large dust particles² rather than those due to just “smog” and other tiny natural aerosols. Large dust particles can not only influence the development of ice at higher temperatures than normal (above -10 C), but is also known to aid the formation of rain due to cloud drops bumping into each other and sticking together; collisions and coalescence because large dust particles can accelerate this process by forming large initial drops at the bottom of the cloud where drops first condense. Here, drops are nearly always too small to bump together and join up unless clouds are deep, like our summer ones, and ice is going to form anyway.

So, yesterday, was a bit of a novelty. Some photos and story telling:

SONY DSC — 1:34 PM. Drizzling from Stratocumulus!

The late Jack Russell, engineer, listening to Art tell another cloud investigation story. — The late Jack Russell, flight engineer, listening to Art tell another cloud investigation story.

2:43 PM. Cumulus humilis field over Saddlebrooke.

3:06 PM. Drizzle precip just a memory. These clouds too shallow to rain. — 3:06 PM. Drizzle precip just a memory. These clouds too shallow to rain via collisions, and too warm to form ice.

Looking ahead….

Mods paint dry weather for the next 15 days, and so yesterday’s disappointing “trace” (don’t recall here that Mr. Cloud Maven person had predicted at least 0.02 inches!) may be it for October. Phooey.

———————-

¹Drizzle: Fine (size range, 200-500 microns in diameter drops) close together, that nearly float in the air. Very difficult to bicycle in drizzle even with a cap or big hat. Fallspeeds, just a few mph. Smaller sizes can’t make it out of the cloud, or evaporate within a few feet almost if they do. Even true drizzle occurrences, you can’t be too far below the base of the clouds or those tiny drops won’t make it down to you.

²What is a “large” dust particle in a cloud? Oh, 1-10 microns in diameter, real rocks compared with the other stuff normally in them. So’s you get a drop that’s already pretty large as soon as condensation takes places. And, if the updrafts are weak at the bottom, then only them big ones might be activated, keeping the whole cloud’s droplet concentrations low! Happens even in places in the middle of huge land masses where in Riyadh, Saudi Arabia, we saw this happen on a dusty, moist day in shallow Stratocumulus clouds. They developed some drizzle drops. I was with the National Center for Atmos. Research on a field project then.

³1988: Rain from Clouds with Tops Warmer than -10 C in Israel (Quart. J. Roy. Meteor. Soc.)

One of the greatest Seattle days in the history of Catalina, Arizona

Yesterday, that is. It felt like I never left. Only 49 F here; was 55 F in Seattle yesterday.

But the main thing that made it seem “so Seattle” was the persistent low Stratocumulus overcast, almost no sun whatsoever, and a little rain. We picked up another 0.03 inches in a couple of morning episodes of R– (an old weather texting¹ shorthand for “very light rain”) to bring the storm total here to 0.55 inches. Of course, the best part of that overcast was that it allowed the ground to be damp for another day, helping the spring grasses and wildflowers by keeping the soil moisture in the soil and not flying away under a hot sun. The worst part of the overcast that lasted almost all day, was that Mr. Cloud Maven person had the day completely wrong–thought it would break open in the afternoon to “partly cloudy” and so he was as gloomy as the sky. You see, as a weather forecaster, you can’t even really enjoy a nice day if you didn’t predict it. Had some sad 75 F days in Seattle when I only predicted 69 F; everybody having summer fun but me.

Enough nostalgia, here are the clouds, even if you have no interest in seeing such boring clouds again:

6:56 AM. Interesting little punctuated lenticular. Mr. CMP has finsihed his blog and thinks the sky will break open in the afternoon. Hah! — 6:56 AM. Interesting little punctuated lenticular. Mr. “CMP” has just finished his long blog and thinks the sky will break open in the afternoon. Hah!

8:00 AM. Stratocumulus tops Samaniego Ridge--with the turrets, you might lean toward adding the descriptor, "castellanus." Note blue sky here, if you didn't see any at all yesterday. — 8:00 AM. Stratocumulus tops Samaniego Ridge–with the turrets, you might lean toward adding the descriptor, “castellanus.” Note blue sky here, if you didn’t see any at all yesterday. No precip evident.

8:02 AM. Looking north toward S-Brooke. Fine shafts of precip emit from Stratocumulus clouds indicating those regions in the cloud where there was more liquid water at one time, where these clouds are humped up like those Sc clouds on Samaniego Ridge. But, was the precip due to ice or the colliding drops process? I wasn't sure at this point. You see, after a storm, the clouds can be real clean, almost oceanic-like meaning they have LOW droplet concentrations, and when the droplet concentrations are low, the drops are usually larger and can get to sizes where they stick together when they collide (think 30-40 micron diameters). You probably have a clue about that size, but it sounds great if you see this and tell a neighbor that, "those clouds might have drops larger than 30-40 micron near cloud tops." Instant expert! — 8:02 AM. Looking north toward S-Brooke. Fine shafts of precip emit from Stratocumulus clouds indicating those regions in the cloud where there was more liquid water at one time, that is, where these clouds are humped up like those Sc clouds on Samaniego Ridge in the prior photo (the precip from those clouds may have been out of sight). But, was the precip shown here due to ice or the colliding drops process? I wasn’t sure at this point. You see, after a storm, the clouds can be real clean, almost oceanic-like meaning they have LOW droplet concentrations, and when the droplet concentrations are low, the drops are usually larger and can get to sizes where they can stick together when they collide (think 30-40 micron droplet diameters). You probably don’t have a clue about those sizes, but it sounds great if you see rain like this and tell a neighbor that, “those clouds might have drops larger than 30-40 microns in diameter near cloud tops.” Instant neighborhood expert!

8:06 AM. Then the clouds to the west of Oro Valley and Catalina began to produce fine precipitation, definitely looking like a true drizzle event (caused by colliding drop rain formation process), at least to me at this point. This is a rare event when very light rain or true misty drizzle (tiny drops, close together) occurs in Arizona. Usually our clouds have too many droplets from natural and anthropogenic sources and the cloud droplets stay too small to collide and stick together, instead bumping around like marbles with all the surface tension they got. — 8:06 AM. Then the clouds to the west of Oro Valley and Catalina began to produce fine precipitation and advance on Catalina. How nice. Definitely was looking like a true drizzle event (caused by colliding drop rain formation process), at least to me at this point. That process is a rare event in AZ when very light rain or true misty drizzle (tiny drops, close together) forms like that. Usually our clouds have too many droplets from natural and anthropogenic sources and the cloud droplets stay too small to collide and stick together, instead bumping around like marbles with all the surface tension they got. And then because they’re all tiny, they don’t have much impact when they hit, there’s not a lot of velocity difference like there would be in a cloud with a broad droplet spectrum, the kind of spectrum we see in “clean” clouds where drops bigger than 30 microns are a plenty. Note trails of precip coming down in center. BTW, to go way off topic, to distract from how bad my forecast was, in “hygroscopic” seeding, particles like salt are introduced at cloud base to encourage the formation of rain through this process in polluted Cumulus clouds. Worked in Saudi, based out of Riyadh, winter of 2006-07, flying in a Lear jet, helping to select Cu for random seeding using that methodology². Our office at the government met building, I recall, was cleaned by the “Bin Laden” group. Hmmmm. Maybe its a common name there, to go even farther off topic.

10:09 AM. So Seattle! (Have to make up for that last bloated caption.)

4:49 PM. And that's your entire day. — 4:49 PM. And that’s your entire day.

6:27 PM. Sunset tried to do something. But, like the day, it was like that sugar icing on a stale cinnamon roll, just didn't quite make it, though cinnamon rolls are quite good as a rule. — 6:27 PM. Sunset tried to do something. But, like the day, it was like that sugar icing on a stale dried out cinnamon roll, just didn’t quite make it, though cinnamon rolls are quite good as a rule.

Today’s clouds

Some residual small Cumulus, maybe clumping into a larger group this morning for a bit, which you would then refer to as Stratocumulus. Should gradually diminish in size and coverage until almost completely clear in the afternoon. Expect a north wind in the afternoon, too.

The weather ahead

There isn’t any, well, not right away, but WAY ahead….

Chances for rain begin to pick up after the 19th as we enter the “zone of curl”, “cyclonic curls” in the upper atmosphere with a lot of “vorticity” in them again, with temperatures falling back to normal values. Pretty tough to have warm weather for long at this time of year in AZ. You see, its troughs like to “nest in the West” in March, April, and May, even when they’re not strong and far enough south to bring rain, maybe only wind. Its a climo thing, and it causes many areas of the West to see an increase in precipitation in March from February, and also halts the rapid rise in spring temperatures (especially in Seattle, hahahaha, sort of).

This because the global circulation pattern, responding to the climb of the sun in the sky and warming continents in the northern hemisphere, those forces acting on the position of the jet stream, and weakening it here in the NH (northern hemisphere), is changing the jet stream pattern so that storms begin to move southeastward from the north Pacific across the Pac NW into the Great Basin area in the spring, bringing cold north Pacific air into the West. There was a great report about this phenomenon by old man Bjerknes out of UCLA with his Ph. D. grad student, Chuck Pyke, back in the mid-1960s. Pyke was a UCLA sports nut, BTW, to add some color to this account.

We won’t see that “trough in the West” pattern for awhile here in our “oasis of warmth” now about to begin, but count on it returning, as it appears to do late in the model runs from last night. Climo is forcing it.

The End, except for footnotes.

——————————————-
¹Yeah, that’s right. Weathermen, as we would say it then, were way ahead of their time, “texting” each other long before kids thought of “texting.” You might write a weather friend, if you could find one: “We had a TSTM to the S with FQTLTGCCCG ALQDS last night for a few H. MVD N.” PIREPS, SIGMETS, too, were all “texted” and texted by teletype! Tell your kids.

²Was under the aegis of Research Applications Program (RAP) at the National Center for Atmospheric Research (NCAR) in Boulder, CO. Money was good…though not nearly as much as you would make as a TEEVEE weather presenter (hahaha). I was a post retiree guest scientist for RAP NCAR. Clouds could be real bumpy there in Saudi, thought I was gonna die once as bottom dropped out of the Lear going into Cumulonimbus at night that one time. Pilot liked to cut it close between the hail shafts and the rising parts of the Cu with little or no precip, using his aircraft radar. But sometimes, it was a little too close…and we got into the shear zone between a strong updraft and the downdraft.

Was it smog or dust? How to tell

OK, climbing down off soapbox today….just don’t read the Hockey Stick Illusion by A. W. Montford unless you want to be upset by some climate scientists pretending to be scientists when they are being something antithetical to science. Reminds me of the 30-odd years of cloud seeding reanalysis experiences I had as a skeptic in that domain. Oops, haven’t climbed completely down yet. Montford should get a Pulitzer for this well documented tale, and his main protagonist, Steve McIntyre, the Rossby Medal or maybe a couple of Nobel Prizes for diligence. Just about off “box” now….but this tale REALLY does remind me of the shenanigans that happened in cloud seeding to repeat myself again and again and again.

It got pretty hazy yesterday afternoon into the time of sunset. This is what it looked like as the sun rotated away from the earth (hahahah). Note the yellowish tinge of the sun. Smog (urban, biomass smoke and hazes, are comprised of smaller aerosol particles, around a 0.01 to 0.1 microns in diameter, whereas dust particles, something that you find around the house everyday here in AZ (to quote Groucho Marx from his quiz program, “You Bet Your Life”) are generally much larger and can extend into sizes of 1-10 microns in diameter. So, in interfering with the transmission of the incoming white sunlight, small aerosol particles in smog take out (scatter) the short wavelengths like the blueish ones) and only the longer wavelengths, the reddish ones, giving the sun an orange or reddish hue. Dust particles, because they are larger, and do not interfere with the short wavelengths of light coming from the as much produce a whitish yellow colored sun. Below yesterday’s sunset is a smokey one from Cuiaba, Brazil, during the burn season, a strawman to show a large, obvious difference. It’s often more subtle than this, so you need to practice labeling sunsets for aerosol sizes. Your neighbors will be impressed.

Since dust particles are larger than smoke particles, they don’t stay afloat as long as smoke particles do, though dust can still drift away from where it was generated before dissipating. It depends on the nature of the surface dust. In Saudi Arabia, dust was often observed without much wind due to the fine nature of the sand (see last photo from Qassim, SA–looks pretty much like pure dust whereas the Catalina sunset suggests dust with smoke due to its more orange coloring).

Factoid: some Gobi Desert dust has impacted the West Coast of the US from time to time!

Clouds? Well, if you looked, you saw a few low cloud shreds called Cumulus fractus (Cu fra) over the Catalinas yesterday afternoon. Some rain fell as close as central AZ as a cold front blew by. But only the cooler air got here. Its 13 deg cooler here than it was yesterday at this time (4:30 AM LST), a sure sign of an air mass change and “fropa” (frontal passage).