1 and wonderful sights were seen yesterday; I could feel the excitement out there as one cloud microstructural mystery after another regaled our Catalina skies.
7:24 AM. Here, a tiny highlighted flake of Altocumulus floating above a mass of light snow/ice crystals, maybe straight below it. This is one the classic mysteries we deal with in “cloud microstructure”; the oddity of nature preferring to generate a droplet before an ice crystal at least to somewhere in the -30°s C. Liquid clouds often are at the top of Altostratus and Nimbostratus (rainy or snowy days) providing the tops aren’t too much colder than -30° C. How strange is it to have liquid water at the lowest temperatures in a cloud system, with all the ice and snow underneath, as shown in this photo (though here they are no longer connected).
7:24 AM/ I think there is itty bitty droplet cloud at the very top bright dot there. A droplet cloud was likely much broader to have produced all the ice we see below that bright dot of liquid cloud.
7:26 AM. Looking afar, to the SW, there’s what appears to be an Altocumulus (droplet cloud) with a few ice crystals underneat it, especially to the right.
How cold are these clouds? Lets look at the TUS sounding, launched at about 3:30 AM yesterday morning.
The TUS rawinsonde balloon data for yesterday morning before dawn. That Altocumulus layer, and the other clouds above were likely at the pinched point above, topping out at -27°C and up around 23,000 feet above sea level (400 millibars), pretty darn cold. But, as you saw in the 3rd photo, not a lot of ice is being generated at this temperature by that patch of Altocumulus clouds to the SW. Not sure why, but its pretty remarkable and that is likely due to small droplet sizes AND a lack of ice nuclei, most of which are known to originate with soil particles When you see these rare occurrences of all or mostly droplet clouds at low temperatures (<-20° C in particular, get ready to see hole punch and ice canals produced by aircraft, a kind of inadvertent cloud seeding.
That bank of Altocumulus was racing at more than 50 mph toward Catalina, and so it got here in a hurry. And, as it got closer, it was also getting more into some airways at that height, possibly descents into PHX since the height of those clouds was below normal jet cruising levels at 23,000 feet Above Sea Level.
7:55 AM. This is one of the strangest sights I have ever seen. Why? On the left side of this photo, the clouds are completely glaciated, composed of ice, while along a line to the right, there’s no sign of ice in Altocumulus clouds that appear to be at the same height (namely, temperature). I have no explanation for this scene, except those involving a lot hand-waving, so we’ll just let go, except that we speculate that the Ac layer was a little lower (warmer)? Could have been.
Now for the aircraft effects. Hardly a few minutes go by before aircraft began marking up this cold Altocumulus layer. Notice that it doesn’t seem to be producing much or any ice on its own, making aircraft inadvertent seeding lines and holes where tremendous numbers of ice crystals are generated immediately present. Here’s the first of many:
8:16 AM. An icy canal due to the passage of an aircraft rips through this pristine layer of Altocumulus whose temperature was around -25° C. The view is looking S toward Tucson, but is unlikely to have been an aircraft landing there because this layer was above 20,000 feet Above Sea Level. An aircraft lanidng at TUS would be much lower, this close. The passage of the aircraft was likely 10 or more minutes before this photo.
8:19 AM. The ice canal is broadening due to turbulence, and ice is not plainly evident to all Cloud Maven Juniors or we will have to go over discerning ice from droplet clouds at the next club meeting.
8:20 AM. A view of the northwest end of this aircraft-produced ice canal. Several others became apparent, too.
Heading for Catalina, this:
9:11 AM. Heading for Catalina, a whole mess of aircraft induced ice in that poor Altocumulus layer. The hole punch was likely due to an aircraft climbing out of or descending into TUS. The age of a hole that large, with ice below it like this would be something of the order of at least half an hour to an hour old. Just behind the hole is a new contrail in the Ac clouds,
9:23 AM. Hole punch area and ice canal arrive over Catalina! Losing control here, taking photo and photo, now looking for stragne optics, usually observed with aircraft produced ice particles because they are so numerous, compete for the available moisture and therefore remain tiny and perfect, prisms, plates, short column ice crystals, ones that can do a lot of optical stuff.
Here’s the south end of that ice canal:
9:24 AM. Also note iconic horse wind vane, and real wind vane atop a personal weather station. Doesn’t everyone have a “PWS”?
Looking straight up at the icy heart of a hole punch region caused by an aircraft. I am sure you have never done this before! This is gonna be a great blog with all these new things for you!
9:27 AM. Look at the detail in the ice, those fine, fine strands! Amazing. The thickest strand might be due to the higher liquiid water in the heart of one of those little Altocumulus cloudlets. ??? Look how much wind shear there is, those little itty bitty ice crystals falling so far behind the parent cloud, the streamers flattening out because the poor little guys, already undersized to begin with, are getting smaller and smaller, the fall velocity getting less and less until the strands are almost horizontal.
9:27 AM. Looking at this gorgeously uniform layer of Altocumulus perlucidus 9honeycomb of elements) translucidus (no shadows). To me this is a phenomenal scene, though maybe to u, not so much, which is understandable.
9:30 AM. The expected intense optical phenomena began to occur in these aircraft contrail remains. Here a parhelia, or sundog. More fireworks in a bit.
9:30 AM. While the parhelia was in its full display, very intense, this was the ice canal passing overhead. Look at the regular spacing of these strands of ice, Might be due to the spacing of the cloudlets in the Altocumulus layer, the spaces between them not producing much ice, or, as we know, contrails tend to clump behind the aircraft likely due to wingtip vortices interacting and combining masses of exhaust water and crud. This is now about an hour and fifteen minutes old, since we saw it way out to the west at 8:16 AM shortly after it formed.
9:37 AM. Here’s what a new aircraft contrail in these clouds looks like, this one about 60 s old looks like. Note all the irregularity in the contrail from the get-go.
As the south end of the original ice canal began to enter the refraction zone for simple ice crystals around the sun, usually at the 22° degree halo position, things began to light up with a particularly bright
circumzenithal arc (more often observed on a halo) or colorful (in this case) partial “reverse halo”. The colors (iridescence) due to the refracting of light within very small ice crystals. Normally iridescence is seen near the sun in Cirrocumulus clouds or the then edges of other droplet clouds. Very exciting.
9:44 AM. A part of a halo curving in the wrong direction, away from the sun! (This is actually called a circumzenithal arc).
9:44 AM. Taking up you up thousands and thousands of feet via a zoomed view. Pretty cool, eh? Notice how much its moved in just seconds, You really have to let your coffee get cold if you’re a photographer and you want to get the best shots of this kind of phenomenon. You really can’t do anything but keep watching every second!
9:44 AM, again. All these changes took place within the minute between 9:44 and 9:45 AM! Here, the next grouping of ice strands is being lit up.
9:48 AM. Just a pretty scene. Altocumulus perlucidus translucidus, pocked with aircraft contrails, if you look real close. Make me move: $1 billion dollars…
9:54 AM. Its not even 10 AM and now this comes along, this fabulously complex zone of CIrrocumulus (at the same level of the Ac clouds) at the tail of the Altocumulus. You can see the much higher Cirrus going crossways, lower center. See TUS sounding for height of Ci.
Then this strange sight:
12:29 PM. A row of Altocumulus or Cirrocumulus, each formed by a little upward bump in the atmosphere of a layer just a hair below saturation. Just rising a few hundred feet or so causes these cloudlets to form. Why aren’t they everywhere? Might be drier. Bumps like this are always present in the atmosphere, especially if there are mountains upwind. Not taken while driving, of course, ; just looks like it thanks to photoshop.
The day closed out with a lower layer of Altocumulus moving in, this layer, according to the TUS sounding, at “only’ -17° C, and little ice detected. Below, at 2:09 PM:
2:09 PM. Altocumulus perlucidus translucidus. A natural conversion to ice is occurring on the right side of the photo.
4:42 PM. So pretty these Altocu.
4:41 PM. A strand of finely patterned Cirrocumulus shot out of the SW as the sun declined.
The Tucson afternoon rawinsonde . launched around 3:30 PM. The Cirrocu in the above photo was likely also at the Cirrus level indicated above.
U of AZ mod thinks so light rain will develop around here in the mid-later afternoon.
1“stragne” above, originally an inadvertent typo, but left in place as another cheap trick to get draw the curiosity of readers who might wonder what stragne is.