I use that expression not only to draw attention to myself since my name is Art, or, “Artie boy” to mom, but also because I had a role in bringing this phenomenon to the attention of the scientific community; that is, that an aircraft could glaciate portions of clouds at temperatures as high as -8°C. This in a peer-reviewed article so controversial it was rejected twice by journal reviewers before “getting in “(pdf here)! Some background on why this happened is found in a footer way down below….
Its common knowledge today that an aircraft can produce in essence a contrail in clouds at temperatures down to about -10°C and must be avoided when researchers are sampling the same cloud over and over at below freezing temperatures.
Back to the beginning:
The day began well enough with a nice sunrise over the Catalinas:
Here’s the early morning National Weather Service balloon sounding from the U of AZ:
Then, as the Altocumulus layer filled in from the west, the aircraft effects roared to life. An example from yesterday, one that passed right overhead of little Catalina!
The weather ahead
More interesting middle and high clouds, probably a great sunset/sunrise or three, but no rain, just virga. The present mass of middle clouds passing over has some virga and sprinkles, but that’s about it from this episode. No real support yet for a change in our dry, warmer than normal weather regime in spaghetti plots though one trough a week or so out is forecast to bring a little rain.
Some background on “APIPs”
This phenomenon had been shot by photographers for decades, yep, DECADES, BUT, it was believed (apparently) by those doing cloud research, that it only happened at very low temperatures such as those when the normal contrails we see occur (at temperatures lower than -35°C), viz., it was ignored.
Another factor was that all of the rare photos of this phenomenon, dubbed “Aircraft Produced Ice Particles” (APIPs, by yours truly, though not the greatest name) appeared in lay or quasi-lay publications and were likely missed by those with big Ph. Ds. who only read technical journals. An example of this was on the cover of the Bulletin of the American Meteorological Society in 1968, a cover shot which drew the greatest amount of reader comments that the journal had ever seen! They went on for a couple of months, some suggesting that the ice and hole in cloud was due to a meteorite!
Also, it was a rare case indeed when the photographer could report the temperature at which it occurred.