Iceland winter photo │ Polar stratospheric cloud │ Glitský
by: Rafn Sig,-
Vogar 2020.01.03 – 10:17:46
Polar stratospheric clouds (PSCs) are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 m (49,000–82,000 ft). They are best observed during civil twilight, when the Sun is between 1 and 6 degrees below the horizon, as well as in winter and in more northerly latitudes. One main type of PSC is made up mostly of supercooled droplets of water and nitric acid and is implicated in the formation of ozone holes. The other main type consists only of frozen ice crystals and is not considered harmful. This type of PSC is also referred to as nacreous (mother of pearl, due to its iridescence).
Due to their high altitude and the curvature of the surface of the Earth, these clouds will receive sunlight from below the horizon and reflect it to the ground, shining brightly well before dawn or after dusk.
PSCs form at very low temperatures, below −78 °C (−108 °F). These temperatures can occur in the lower stratosphere in polar winter. In the Antarctic, temperatures below −88 °C (−126 °F) frequently cause type II PSCs. Such low temperatures are rarer in the Arctic. In the Northern hemisphere, the generation of lee waves by mountains may locally cool the lower stratosphere and lead to the formation of lenticular PSCs.
. . . If you would like to join my team of Documenting Iceland, You are welcome: . . . https://www.patreon.com/RafnSig
You can buy this and other photos at my Icelandic Stock Photo Web: IceStockPhotos.com