The stratosphere above the Arctic Circle is getting cold... very cold. That is the only way to explain the heart-shaped cloud that appeared yesterday in Abisko, Sweden.
«We were eating lunch when one of our aurora tour guides saw it out the window. The entire restaurant emptied out as we all went outside for a better view,» said the author of the image Chad Blakley, a member of the Lights over Lapland project.
© Chad Blakley
The stratosphere is usually cloud-free (completely transparent) due to the fact that it is very dry with sparse widely separated water molecules. However, when the temperature drops to −85ºC, these sparse molecules begin to reluctantly gather, forming ice crystals that turn into polar stratospheric clouds (PSC).
Polar stratospheric clouds are famous for their pastel colors. Some consider them to be the most beautiful clouds on Earth. «I can’t argue with that. Our first PSC of the season was a beauty!» Blakley said.