As 2019 came to a close, northern Europe saw a beautiful display of polar stratospheric clouds. They are high-altitude clouds, seen at heights between 49,000 and 82,000 feet (15,000–25,000 meters). The sort made of frozen ice crystal are also called nacreous clouds or mother-of-pearl clouds. In describ ing them, Les Cowley at Atmospheric Optics said they are:
… rare, but once seen are never forgotten. They are mostly visible within two hours after sunset or before dawn when they blaze unbelievably bright with vivid and slowly shifting iridescent colours.
According to Tony Phillips at Spaceweather:
Polar stratospheric clouds are newsworthy because normally the stratosphere has no clouds at all. The stratosphere is arid and almost always transparent. Only when the temperature drops to a staggeringly cold -85C can sparse water molecules assemble themselves into icy stratospheric clouds.
PSCs are far more rare than auroras.
We received several photos of polar stratospheric clouds this week, and more appear in Spaceweather.com’s gallery. The image above – and video below – from Göran Strand in Sweden are among the best we saw. Thank you, Göran!
Bottom line: As 2019 ended, northerly latitudes saw a beautiful display of polar stratospheric clouds.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.