Observers report about the outbreak of polar stratospheric clouds around the Arctic circle. “On 13 February, the sky was filled with their bright colors from sunrise to sunset,” says MIA Stalnacke, remembering polar stratospheric clouds at Kiruna, Sweden. These unusual clouds were also observed throughout Finland, according to Matti Helin photographed the phenomenon on February 13.
These clouds, which are sometimes called night-shining clouds are the highest clouds of the Earth. It’s a very cold, very sparse and filled with tiny ice crystals clouds hovering at the altitude of about 80 kilometers above the surface of our planet. When the sun rays pass through these ice crystals, clouds are becoming a rich glowing blue color, clearly visible in a deep twilight.