Wednesday, December 17, 2008
Punch Hole Clouds And Other Rarely Seen Cloud Formations
Punch Hole Clouds may appear as a circular or oval holes in a layer of supercooled clouds; sometimes they assume a form of a perfect circle and persist for quite a long time, drifting together with the cloud layer. One explanation seems to blame the air traffic (the jet contrail intersections) combined with a thermal inversion (a circular motion of a rising warm air).
It seems both rising and sinking air currents can create the same effect. Sometimes a very stable, uniform layer of high-altitude clouds can get "punched though" by a pocket of cold air, which sinks toward the ground - creating the circular hole formation.
NASA Terra satellite equipped with the Moderate Resolution Imaging Spectroradiometer (MODIS) has captured these images over Acadiana area in southern Louisiana - a splattering of round holes actually stretched over several states: Oklahoma, Arkansas, Louisiana, and Texas. Some were elongated, some appeared to have smaller clouds inside them.
"This strange phenomenon resulted from a combination of cold temperatures, air traffic, and perhaps unusual atmospheric stability. The cloud blanket on January 29 consisted of supercooled clouds. Supercooled clouds contain water droplets that remain liquid even though the temperature is well below freezing, and such clouds are not unusual. As aircraft from the Dallas-Fort Worth airport passed through these clouds, tiny particles in the exhaust came into contact with the supercooled water droplets, which froze instantly. The larger ice crystals fell out of the cloud deck, leaving behind the “holes,” while the tiniest ice particles in the center remained aloft." (source)