A number of spectacular polar stratospheric clouds have been visible around the Arctic this week. These clouds are very colorful. Unlike normal grey-white clouds, which hug Earth’s surface at altitudes of only 5 to 10 km, polar stratospheric clouds float through the stratosphere (25 km).
Polar stratospheric clouds photographed over Tromsø, Norway. Image credit: Truls Tiller
Image credit: Truls Tiller
Truls Tiller photographed these incredible clouds over Tromsø, Norway, on Dec. 16th. “Here the sun is gone for now,” says Tiller, “but this beautiful view makes the winter darkness nice to be in as well. The picture was taken at 10.30 am, in the middle of the ‘day.'”
Polar stratospheric clouds or PSCs, also known as nacreous clouds from nacre, or mother of pearl, due to its iridescence), are clouds in the winter polar stratosphere.
Image credit: Truls Tiller
Image credit: theozonehole.com
PSCs form at very high altitudes, between 15 and 25 km (about 50,000 to 80,000 feet). PSCs only form at very cold temperatures around -78° C (-108° F). Sometimes, in winter near the North or South Pole, temperatures in the lower stratosphere get that cold. That’s when PSCs can form.
PSCs were long regarded as curiosities and of no real consequence, nut is has been observed that these clouds are now known as sites of harmful destruction of stratospheric ozone over the Antarctic and Arctic.
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