Distrails over Central Europe
A distrail, short for dissipation trail, forms when an aircraft flies through a supercooled cloud.
22 September 2022
28 December 2016
By HansPeter Roesli (Switzerland) and Jochen Kerkmann (EUMETSAT) and Djordje Gencic (RHMSS)
A holepunch cloud is a large gap, usually circular or elliptical, that can appear in cirrocumulus or altocumulus clouds. They form when part of the cloud layer forms ice crystals which are large enough to fall as a 'fallstreak'.
They result from a combination of cold temperatures, air traffic, and atmospheric instability. The holes form in clouds of supercooled water droplets, water below 0°C but not yet frozen. These water droplets need a tiny particle, a nucleus, to freeze or to be cooled below -40°C.
Using Himawari-8 imagery it was possible to clearly see these holes that developed over China, see the Himawari-8 Cloud Phase RGB, (NIR1.6-NIR2.3-VIS0.5), 28 December 02:20 UTC (Figure 1).
The animated gif of Himawari-8 visible imagery, 28 December 01:00–06:00 UTC (Figure 2), shows the very fast evolution of these features over couple of hours.
The radiosounding of Nanjing (from University of Wyoming) indicated the probable height of these clouds, namely 350hPa (about 8400m).
On the AHI Convection RGB, 28 December 14:00 UTC (Figure 3) the distrails are seen very clearly, with good contrast.
Punching Through (NASA Earth Observatory)