Earth's stratosphere is normally free of clouds. Not this weekend, though. Observers around the Arctic Circle are reporting an outbreak of brilliantly-colored icy clouds in the typically dry and transparent layer of our planet's atmosphere. Eric Fokke photographed the display on New Years Eve from the Lofoten Islands of Norway:
© Eric Fokke
These icy clouds are a sign of very cold temperatures. For ice crystals to form in the arid stratosphere, temperatures must drop to around -85º C. High-altitude sunlight shining through tiny ice particles ~10µm across produce the characteristic bright iridescent colors.

Once thought to be mere curiosities, some polar stratospheric clouds (PSCs) are now known to be associated with the destruction of ozone. Indeed, an ozone hole formed over the UK in Feb. 2016 following an outbreak of ozone-destroying Type 1 PSCs.

These clouds really are as amazing as they look in Fokke's photo. They have much more vivid colors than ordinary iridescent clouds, which form closer to Earth in the troposphere. Once seen, a stratospheric cloud is never forgotten.
© Eric Fokke

© Eric Fokke