Polar stratospheric clouds are of two types — good and bad

This week observers of the Arctic sky, admired the latest outbreak of polar stratospheric or nacreous, clouds. Some call them "fluorescent lights" because of the bright iridescent colors. However, polar stratospheric clouds are of two types, and the second is not so beautiful and even harmful. Both species are depicted in this photograph taken on January 25 Rauno Pakarinen from pieksämäki, Finland.

Beautiful and harmless clouds are high and are composed of water ice.

Ominous yellow haze, visible at the bottom, is also polar stratospheric clouds, also called cloud type I. They consist of tiny drops of nitric, sulphuric acids and other compounds. The surface of these droplets act as catalysts, transforming the relatively soft forms of anthropogenic chlorine into active free radicals capable of destroying ozone. These clouds form the ozone hole letting in harmful UV radiation at the Earth's surface.

Usually polar stratospheric clouds appear within the far North. But the terrain in the photo located to the South of Lapland, which is quite a rarity.

Translated by «Yandex.Translator»