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 |
A polar stratospheric cloud (PSC) is a cloud that forms in the winter polar stratosphere at altitudes from 15,000 to 25,000 m (49,000 to 82,000 ft). They are best observed during civil twilight, when the Sun is between 1° and 6° below the horizon, as well as in winter and in more northerly latitudes. One main type of PSC is composed of mostly supercooled droplets of water and nitric acid and is implicated in the formation of ozone holes. The other main type consists only of ice crystals, which are not harmful. This type of PSC is also called nacreous (/ˈneɪkriəs/; from nacre, or mother of pearl), due to its iridescence.