Dust in the wind; model rain on the distant horizon

“All it was was dust in the wind” , recalling that tuneful song about large aerosol particles by the rock group, Kansas. Note: Their first album was incredible! (This lead in, in case you thought that yesterday evening’s haze was smoke from our awful fires.)

Here’s the change from two evenings ago to last evening. Cold front went by late yesterday afternoon, pressure began to rise, the dust moved in, and temperatures were 5-7 degrees cooler than it was at the same time the day before. I guess we only get dirt now with our fronts. I guess we should be happy; we have that bit more top soil as well a lower temperatures for a day or so. BTW, dust particles causing this gritty haze at right usually run a few micrometers in size, HUGE for aerosol particles, so, unlike smoke particles, mostly 100 times smaller, dust don’t hang around for long.

A happy surprise in the overnight National Center for Environment (NCEP) model run, as shown repackaged by IPS Meteorstar a nice weather browsing web site. Water from the sky in the model runs! Right here in SE Arizona! Its only 12 days away! Start your calendars! It wasn’t there on the prior NCEP run! (Sad, “truth in advertising” note: These forecasts are mostly unreliable this far in advance, but…what the HECK! It feels great to see possibly bogus rain here and let the mind wander toward the presence of giant Cumulus clouds, ones that transition into Cumulonimbus capillatus incus ones, cloud to ground lightning, the aforementioned dust washed off the cacti and mesquite trees, fires put out by gully washers! Its like thinking about Christmas or other gift receiving holiday! OK, calming down now. Could just be a numerical mirage. We have to keep that in mind. Feet on ground now. Not having unrealistic expectations as I sometimes do.

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.

The Twelve…rain drops in Catalina, that is

Well, maybe there were about 27, but anyway….not very many; still, those drops were to be treasured after not seeing a single “hydrometeor” display in SE AZ in so–ooooo LONG A TIME!

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PG-13 advisory; DRIZZLE is discussed

I have to warn you at this point. That rain event yesterday WAS NOT DRIZZLE!!!!!!!!!!!!!!!!!!!!!!!!!!! I will be ROYALLY PO-ed if I hear someone in my social network or a TEEVEE weather presenter say that it “drizzled” yesterday!

Why make a BIG THING out of the correct type of precipitation?

I have to tell you a true story (well, I don’t have to, but I am going to anyway) about the importance of drizzle (i. e., fine, close together drops that appear to FLOAT in the air). This event happened during my cloud seeding “vigilante” adventures (see Publications for samples). A well-known professor of cloud seeding in a foreign country asked me to leave his office and never come back after I told him it had been “drizzling” outside, “10s per liter” in the air.

Drizzle is a profound indicator of cloud structure overhead, and the presence of drizzle falling from the clouds in that professor’s region’s meant his numerous reports of how clouds were, ripe for cloud seeding, were in substantial error. So you can understand why a report of true “drizzle” would naturally be upsetting to that professor. Man, am I digressing here! Yikes. My apologies. (BTW, those reports WERE in error, confirmed by aircraft years later! (Spiking football now, with a proper amount of decorum, of course!)

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OK, back on task….

With the sky full of low (“boundary layer”) clouds by mid-day (f you’ve forgotten, that was yesterday, May 10th, 2011) and with RW— in the air (“triple minus”, extremely light rain showers) by 1:30 PM, with gusty winds, temperatures in the mid-60s, it turned out to be quite a “storm.” It just as well could have been but a mostly sunny day with just a scattered Cumulus clouds here and there the way some models were “telling it.”

Here’s a pictorial on how it went, from a Catalina, AZ, perspective:

1) 09:29 AM, itty bitty Cumulus (Cumulus “fractus”) starting to appear,

2) 12:03 PM, larger Cumulus growing up into Cumulus “mediocris” beyond Tortolita Mountains on the horizon,

3) 12:29 PM, virga and rain visible to the NW horizon! Now I am getting apoplectic since the best models in the world did not have this precipitation over thataway! But there it is, bigger than watermelons. The models have to be really red-faced about this! Not everything in the world is predetermined by numerical models; you can say things that might be right and those models are WRONG! Just like in the 1970s when a lot people thought global cooling was underway and that’s where we were headed! But they were WRONG! Who were those clowns anyway?! (hahaha, sort of).

4) 1:25 PM. Now where was I before all that excitement? Oh, yeah. Here’s some ice for you. See the frizzy top parts of this cloud in the center of this photo above the dead tree that the birds like to sit in? Well, them’s ice crystals, and likely snowflakes that have formed in that medium-sized Cumulus cloud (above the dead tree) and its in the upwind direction. Behind that is more ice and precip falling from a wide area of a Cumulus-Stratocumulus complex.

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Mini-diversion

Quiz. How cold does the top of THAT cloud have to be to look like that (have that much ice in it, probably a few per liter to maybe 10 or so, not a tremendous amount but significant)? Well, with bases as cold as they were, near freezing by this time of day at around 7, 000 feet above the ground or 10, 000 feet above sea level, around -15 C (or about 5 F). Amaze your friends with cloud trivia like this! Well, maybe not.

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5) 1:25 PM. Here it is, a band of precipitating clouds overhead. Now the ONLY question remaining, as you gaze upwind at Twin Peaks clearly visible through the precip and virga is, how much will there be? None? Or as much as a “trace”? Measurable is out of the question, looking at this scene below the clouds. Most of the visibility degradation is due to dusty air, not precip. Darn. (Amaze your friends with skills like this! Well, maybe not.)

6) 3:03 PM. The End is Near

7) 7:06 PM. Nice sunset with traces of Cirrus and Ac len on the horizon, driblets from a storm striking the Pac NW. Isn’t there always a storm striking the Pac NW? I digress again.

Man, I could go on about the weather maps of yesterday, but will quit here.

The end.

If you REALLY want to see how it went, take a look at the U of A time lapse video here.

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).

Catalina-Smog before the storm

Those of us awaking this morning were literally a-palled by the amount of smoke around. Not even Twin Peaks was visible, some 10 miles to the SW. See examples of smog in the photos below.

Where did it come from? Back trajectories, ones that end in Tucson as of this morning at 5 AM shown below, suggest the smog came from the SE of us (red and blue lines. The green line for air around 12,000 feet, represents where the air came from that air came from the off the California coast ; it was too high to be involved in our smog episode. Best guess, could be smog from El Paso and/or from burning in northern Mexico, that in the presence of light winds, has kind of muddled around and drifted N into Tucson.

Note the pooling of smoke in the low valley ahead in the Golder Ranch area in the first photo. Probably the result of wood-burning stoves used in the small housing development back there. What it shows you is the persistent nighttime inversion that forms in that bowl, the flat top of the smoke indicating a temperature inversion. You then see a “clear slot” of little smog and then the overall deeper smog layer above that, also very laminar in appearance. With the sun’s rise over the mountain, that kind of structure/separation is soon removed as bubbles of warmer surface air float upward and are replaced by downward moving blobs, mixing all the structure you see in the first photo out. In the last photo, a few tiny cumulus fractus clouds composed of droplets have formed over the Catalina Mountains. The droplets in those clouds are probably 10 microns in diameter (about 1/10 the size of a human hair). These droplets are about 100-1000 times bigger than the aerosol particles making up the smog. This makes the clouds to tell from transparent haze blobs because the smog particles are too small to scatter much light while the cloud particles even in small clouds, prevent you from seeing through them. Well something like that.

Hang on to your hat tomorrow; windy, thinking momentary gusts here in “Catalina Heights” will hit 30-50 mph by late afternoon and overnight before a very strong cold front rolls through around dawn tomorrow. This is an unusually strong upper level AND lower level system with a deep low expected to form over southern Nevada during the day tomorrow. Looks like the rain could change to snow above 3,000 feet after the front goes through, too. That would be terrific! The clearing after the front goes by will probably be late in the day with passing light showers possible until early Friday morning. The ones later in the day and overnight, are likely to be snow flurries above 3,000 feet . Don’t expect the temperature to do much tomorrow. And, the amounts of precip are likely to be substantial putting us at or above normal for the month. Yay! Well, this what it looks like to me; check the NWS for the official forecast!