Editing Cirrus cloud (section)

== Description ==
{{multiple image
| perrow            = 2
| total_width       = 500
| caption_align     = center
| align             = right
| image_style       = border:none;
| image1            = Cirrus castellanus.jpg
| caption1          = Cirrus castellanus
| image2            = Cyrus Cloud above Balepanjang - Wonogiri, Central Java. Indonesia.jpg
| caption2          = Cirrus fibratus
| image3            = Cirrus floccus with virga 001.jpg
| caption3          = Cirrus floccus
| image4            = Cirrus spissatus cumulonimbogenitus in Oklahoma.jpg
| caption4          = Cirrus spissatus
| image5            = Cirrus clouds 011.jpg
| caption5          = Cirrus uncinus, commonly called [[mare]]'s tails
| image6            = Cirrus o zachodzie.jpg
| alt6              = A picture of contorted cirrus cloud shining red in the sunset. Fall streaks (like long thin streamers) descend from the clouds.
| caption6          = Fall streaks in a cirrus cloud
| header            = Species of cirrus clouds
}}

Cirrus are wispy clouds made of long strands of ice crystals that are described as feathery,<ref name="cloud-classification">{{cite web |last=Funk |first=Ted |title=Cloud Classifications and Characteristics |url=https://www.weather.gov/media/lmk/soo/cloudchart.pdf |archive-url=https://web.archive.org/web/20141127023644/http://www.crh.noaa.gov/lmk/soo/docu/cloudchart.pdf |archive-date=27 November 2014 |access-date=23 February 2022 |work=The Science Corner |publisher=[[National Oceanic and Atmospheric Administration|NOAA]] |page=1}}</ref> hair-like, or layered in appearance.<ref name="MetOffice" /> First defined scientifically by [[Luke Howard]] in an 1803 paper,<ref>
{{cite book |last=Howard |first=Luke |author1-link=Luke Howard |date=1865 |title=Essay on the Modifications of Clouds |url=https://books.google.com/books?id=toU-AAAAYAAJ |location=London |publisher=[[Churchill_Livingstone|John Churchill & Sons]]|page=3|edition=3rd |orig-date=1803}}</ref> their name is derived from the [[Latin]] word ''cirrus'', meaning 'curl' or 'fringe'.<ref>{{cite OED 1933|Cirrus}}</ref> They are [[Transparency and translucency|transparent]], meaning that the sun can be seen through them. Ice crystals in the clouds cause them to usually appear white, but the rising or setting sun can color them various shades of yellow or red.<ref name="MetOffice" /><ref name="JetStream">{{cite web|url=https://www.weather.gov/jetstream/basicten|title=Ten Basic Clouds|publisher=National Oceanic and Atmospheric Administration|website=National Weather Service: Jetstream|access-date=17 March 2022|archive-date=21 May 2022|archive-url=https://web.archive.org/web/20220521143550/https://www.weather.gov/jetstream/basicten|url-status=live}}</ref> At [[dusk]], they can appear gray.<ref name="JetStream" />

Cirrus comes in five visually-distinct species: [[Cirrus castellanus|castellanus]], [[Cirrus fibratus|fibratus]], [[Cirrus floccus|floccus]], [[Cirrus spissatus cloud|spissatus]], and [[Cirrus uncinus cloud|uncinus]]:<ref name="MetOffice">{{cite web|url=https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/clouds/high-clouds/cirrus|title=Cirrus clouds|publisher=Meteorological Office of the UK|access-date=23 February 2022|archive-date=23 February 2022|archive-url=https://web.archive.org/web/20220223181646/https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/clouds/high-clouds/cirrus|url-status=live}}</ref>

* Cirrus castellanus has cumuliform tops caused by high-altitude convection rising up from the main cloud body.<ref name="MetOffice" /><ref name="audubon-446">{{harvnb|Audubon|2000|p=446}}</ref>
* Cirrus fibratus looks striated and is the most common cirrus species.<ref name="MetOffice" /><ref name="audubon-446" />
* Cirrus floccus species looks like a series of [[wikt:tuft|tufts]].<ref>{{cite web|url=https://cloudatlas.wmo.int/en/species-cirrus-floccus-ci-flo.html|title=Cirrus floccus (Ci flo)|publisher=World Meteorologizal Organization|website=International Cloud Atlas|access-date=19 March 2022|archive-date=19 March 2022|archive-url=https://web.archive.org/web/20220319171039/https://cloudatlas.wmo.int/en/species-cirrus-floccus-ci-flo.html|url-status=live}}</ref>
* Cirrus spissatus is a particularly dense form of cirrus that often forms from thunderstorms.<ref>{{cite web|url=https://cloudatlas.wmo.int/en/species-cirrus-spissatus-ci-spi.html|title=Cirrus spissatus (Ci spi)|publisher=World Meteorological Organization|website=International Cloud Atlas|access-date=19 March 2022|archive-date=3 May 2022|archive-url=https://web.archive.org/web/20220503184137/https://cloudatlas.wmo.int/en/species-cirrus-spissatus-ci-spi.html|url-status=live}}</ref>
* Cirrus uncinus clouds are hooked and are the form that is usually called mare's tails.<ref name="audubon-446" /><ref>{{cite news|url=https://www.bbc.com/weather/features/36702877|title=Cloud-busting: Mares' Tails|access-date=15 March 2022|date=4 July 2016|work=BBC Weather|publisher=[[British Broadcasting Corporation]]|archive-date=15 March 2022|archive-url=https://web.archive.org/web/20220315123651/https://www.bbc.com/weather/features/36702877|url-status=live}}</ref>

Each species is divided into up to four varieties: [[Cirrus intortus cloud|intortus]], [[Cirrus vertebratus|vertebratus]], [[Cirrus radiatus|radiatus]], and [[Cirrus duplicatus|duplicatus]]:<ref>{{cite web|url=https://cloudatlas.wmo.int/en/varieties-cirrus-ci.html|title=Cirrus – Varieties|website=International Cloud Atlas|access-date=23 February 2022|archive-date=3 May 2022|archive-url=https://web.archive.org/web/20220503184135/https://cloudatlas.wmo.int/en/varieties-cirrus-ci.html|url-status=live}}</ref>

* Intortus variety has an extremely contorted shape, with [[Kelvin–Helmholtz instability|Kelvin–Helmholtz waves]] being a form of cirrus intortus that has been twisted into loops by layers of wind blowing at different speeds, called [[wind shear]].<ref name="audubon-446" />
* Radiatus variety has large, radial bands of cirrus clouds that stretch across the sky.<ref name="audubon-446" />
* Vertebratus variety occurs when cirrus clouds are arranged side-by-side like ribs.<ref>{{cite web|url=https://glossary.ametsoc.org/wiki/Vertebratus|title=Vertebratus|access-date=17 March 2022|publisher=American Meteorological Society|website=Glossary of Meteorology|archive-date=17 March 2022|archive-url=https://web.archive.org/web/20220317211240/https://glossary.ametsoc.org/wiki/Vertebratus|url-status=live}}</ref> 
* Duplicatus variety occurs when cirrus clouds are arranged above one another in layers.<ref>{{cite web|url=https://glossary.ametsoc.org/wiki/Duplicatus|title=Duplicatus|access-date=17 March 2022|publisher=American Meteorological Society|website=Glossary of Meteorology|archive-date=3 May 2022|archive-url=https://web.archive.org/web/20220503184135/https://glossary.ametsoc.org/wiki/Duplicatus|url-status=live}}</ref>

Cirrus clouds often produce hair-like filaments called [[fall streak]]s, made of heavier ice crystals that fall from the cloud. These are similar to the [[virga]] produced in liquid–water clouds. The sizes and shapes of fall streaks are determined by the wind shear.<ref name="Illinois-University">{{cite web|title=Cirrus Clouds: Thin and Wispy|url=http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/cld/cldtyp/hgh/crs.rxml|work=Cloud Types|publisher=Department of Atmospheric Sciences at University of Illinois|access-date=29 January 2011|archive-date=25 November 2010|archive-url=https://web.archive.org/web/20101125044054/http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/hgh/crs.rxml|url-status=live}}</ref>

Cirrus cloud cover varies [[diurnal cycle|diurnally]]. During the day, cirrus cloud cover drops, and during the night, it increases.<ref name="heymsfield-2-4" /> Based on [[CALIPSO]] satellite data, cirrus covers an average of 31% to 32% of the Earth's surface.<ref name="gasparini-1987">{{harvnb|Gasparini|Meyer|Neubauer|Münch|2018|p=1987}}</ref> Cirrus cloud cover varies wildly by location, with some parts of the tropics reaching up to 70% cirrus cloud cover. Polar regions, on the other hand, have significantly less cirrus cloud cover, with some areas having a yearly average of only around 10% coverage.<ref name="heymsfield-2-4">{{harvnb|Heymsfield|Krämer|Luebke|Brown|2017|p=2.4}}</ref> These percentages treat clear days and nights, as well as days and nights with other cloud types, as lack of cirrus cloud cover.<ref name="gasparini-1985">{{harvnb|Gasparini|Meyer|Neubauer|Münch|2018|p=1985}}</ref>