POLAR STRATOSPHERIC CLOUDS:
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.
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.
Eric Fokke photographed the display on New Years Eve from the Lofoten Islands of Norway