Polar stratospheric cloud

Polar stratospheric cloud
Antarctic stratospheric cloud (nacreous clouds)
Abbreviation	PSC
Altitude	15,000–25,000 m (49,000–82,000 ft)
Classification	Other
Appearance	Glowing brightly with vivid iridescent colors
Precipitation	No

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.^[1] 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.^[2] The other main type consists only of ice crystals which are not harmful. This type of PSC is also referred to as nacreous (/ˈneɪkriəs/, from nacre, or mother of pearl, due to its iridescence).