Editing Polar stratospheric cloud (section)

{{short description|Clouds occurring in the stratosphere in high-latitude regions}}
{{Infobox Cloud
| name           = Polar stratospheric cloud
| image location = Nacreous clouds Antarctica.jpg
| image name     = Antarctic stratospheric cloud (nacreous clouds)
| abbreviation   = PSC
| symbol         =
| genus          =
| species        =
| variety        =
| altitude_m     = 15,000–25,000
| altitude_ft    = 49,000–82,000
| level          = other
| appearance     = Glowing brightly with vivid [[Cloud iridescence|iridescent]] colors
| precipitation  = No
| thickness      = 
| Ice content    = 
}}
[[File:Polar stratospheric cloud seen from Brissago, Ticino, Switzerland.jpg|alt=First documented appearance of a polar stratospheric cloud over Switzerland and Italy, seen from Brissago, Ticino, Switzerland|thumb|First documented appearance of a polar stratospheric cloud over Switzerland and Italy, seen from Brissago, Ticino, Switzerland on December 22, 2023]]

A '''polar stratospheric cloud''' ('''PSC''') is a [[cloud]] that forms in the winter polar [[stratosphere]] at altitudes from {{cvt|15000|to|25000|m|ft|sp=us}}. They are best observed during [[Twilight#Civil twilight|civil twilight]], when the [[Sun]] is between [[angular distance|1° and 6° below]] the [[horizon]], as well as in [[winter]] and in more northerly latitudes.<ref name=AAD /> One main type of PSC is composed of mostly [[supercooling|supercooled]] droplets of water and [[nitric acid]] and is implicated in the formation of [[ozone depletion|ozone holes]].<ref>{{cite web |publisher=[[United States Environmental Protection Agency|EPA]] |url=https://epa.gov/ozone/science/hole/whyant.html#psc |archive-url=https://web.archive.org/web/20060930070256/http://epa.gov/ozone/science/hole/whyant.html#psc |archive-date=2006-09-30 |title=Why is the ozone hole over Antarctica?}}</ref> The other main type consists only of [[ice crystal]]s, which are not harmful. This type of PSC is also called '''nacreous''' ({{IPAc-en|ˈ|n|eɪ|k|r|i|ə|s}}; from ''nacre'', or [[mother of pearl]]), due to its [[cloud iridescence|iridescence]].