Editing Cirrus cloud

{{Short description|Genus of atmospheric cloud}}
{{Use dmy dates|date=March 2022}}
{{Featured article}}
[[File:CirrusField-color.jpg|thumb|upright=1.6|alt=A picture of a bright blue sky with many different types of white cirrus clouds. The clouds are over a grassy field with a line of trees in the distance.|Sky containing different types of cirrus clouds]]
'''Cirrus''' ([[list of cloud types|cloud classification]] symbol: '''Ci''') is a [[Cloud#Levels and genera|genus]] of high [[cloud]] made of ice [[crystals]]. Cirrus clouds typically appear delicate and wispy with white strands. In the Earth's atmosphere, cirrus are usually formed when warm, dry air rises, causing [[water vapor]] [[Deposition (phase transition)|deposition]] onto mineral dust and metallic particles at high altitudes. Globally, they form anywhere between {{convert|4000|and|20000|m|ft|abbr=off|sp=us}} above [[sea level]], with the higher elevations usually in the [[tropics]] and the lower elevations in more [[Polar regions of Earth|polar regions]].

Cirrus clouds can form from the tops of [[cumulonimbus cloud|thunderstorms]] and [[tropical cyclone]]s and sometimes predict the arrival of [[precipitation|rain]] or storms. Although they are a sign that rain and maybe storms are on the way, cirrus themselves drop no more than [[virga|falling streak]]s of ice crystals. These crystals dissipate, melt, and evaporate as they fall through warmer and drier air and never reach ground. The word ''cirrus'' comes from the [[Latin]] prefix ''cirro-'', meaning "tendril" or "curl".<ref name="cloud-class">{{cite web|url=http://www.crh.noaa.gov/lmk/?n=cloud_classification|title=Cloud Classification|access-date=2 January 2014|publisher=National Weather Service}}</ref> Cirrus clouds warm the earth, potentially contributing to [[climate change]]. A warming earth will likely produce more cirrus clouds, potentially resulting in a [[climate change feedback|self-reinforcing loop]].

[[Optical phenomena]], such as [[sun dog]]s and [[halo (optical phenomenon)|halos]], can be produced by light interacting with ice crystals in cirrus clouds. There are two other high-level cirrus-like clouds called [[cirrostratus]] and [[cirrocumulus]]. Cirrostratus looks like a sheet of cloud, whereas cirrocumulus looks like a pattern of small cloud tufts. Unlike cirrus and cirrostratus, cirrocumulus clouds contain droplets of [[supercooling|supercooled]] (below [[freezing point]]) water.

Cirrus clouds form in the atmospheres of [[Atmosphere of Mars|Mars]], [[Atmosphere of Jupiter|Jupiter]], [[Saturn#Atmosphere|Saturn]], [[Atmosphere of Uranus|Uranus]], and [[Neptune#Atmosphere|Neptune]]; and on [[Atmosphere of Titan|Titan]], one of Saturn's larger moons. Some of these [[Extraterrestrial atmosphere|extraterrestrial]] cirrus clouds are made of [[ammonia]] or [[methane]], much like water ice in cirrus on Earth. Some [[interstellar cloud]]s, made of grains of [[cosmic dust|dust]] smaller than a thousandth of a millimeter, are also called ''cirrus''.

== Description ==
{{multiple image
| perrow            = 2
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| 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>

== Formation ==
Cirrus clouds are usually formed as warm, dry air rises,<ref name="MetOffice" /> causing water vapor to undergo [[Deposition (phase transition)|deposition]] onto particles, including mostly mineral dust and metallic particles<ref name =sciart/><ref name="cirrus-origins">{{cite web|url=
https://csl.noaa.gov/news/2013/139_0509.html|title=The origins of cirrus: Earth's highest clouds have dusty core|date=9 May 2013|access-date=17 March 2022|website=NOAA Research|publisher=National Oceanic and Aerospace Administration|archive-date=21 May 2022|archive-url=https://web.archive.org/web/20220521143550/https://research.noaa.gov/article/ArtMID/587/ArticleID/1503/The-origins-of-cirrus-Earth%E2%80%99s-highest-clouds-have-dusty-core|url-status=live}}</ref> at high altitudes. Particles gathered by research aircraft from cirrus clouds over several locations above North America and Central America included mineral dust (containing aluminum, potassium, calcium, iron, and silicon), metallic particles in elemental, sulfate and oxide forms (containing sodium, potassium, iron, nickel, copper, zinc, tin, silver, molybdenum and lead), possible biological particles (containing oxygen, carbon, nitrogen and phosphorus) and elemental carbon. The authors concluded that mineral dust contributed the largest number of ice nuclei to cirrus cloud formation.<ref name =sciart>{{cite journal | url=https://www.science.org/doi/10.1126/science.1234145 | doi=10.1126/science.1234145 | title=Clarifying the Dominant Sources and Mechanisms of Cirrus Cloud Formation | date=2013 | last1=Cziczo | first1=Daniel J. | last2=Froyd | first2=Karl D. | last3=Hoose | first3=Corinna | last4=Jensen | first4=Eric J. | last5=Diao | first5=Minghui | last6=Zondlo | first6=Mark A. | last7=Smith | first7=Jessica B. | last8=Twohy | first8=Cynthia H. | last9=Murphy | first9=Daniel M. | journal=Science | volume=340 | issue=6138 | pages=1320–1324 | pmid=23661645 | bibcode=2013Sci...340.1320C | url-access=subscription }}</ref>

The average cirrus cloud altitude increases as [[latitude]] decreases, but the altitude is always capped by the [[tropopause]].<ref name="D&R-973" /> These conditions commonly occur at the leading edge of a [[warm front]].<ref name="audubon-447"/> Because [[absolute humidity]] is low at such high altitudes, this genus tends to be fairly transparent.<ref name="usatoday">{{cite news |url=https://www.usatoday.com/weather/wcirrus.htm |title=Cirrus Clouds |last=Palmer |first=Chad |access-date=13 September 2008 |work=[[USA Today]] |date=16 October 2005|archive-url= https://web.archive.org/web/20081108034842/https://www.usatoday.com/weather/wcirrus.htm |archive-date= 8 November 2008}}</ref> Cirrus clouds can also form inside [[fallstreak hole]]s (also called "cavum").<ref>{{cite web|url=https://cloudatlas.wmo.int/en/clouds-supplementary-features-cavum.html|title=Cavum|access-date=26 September 2022|publisher=World Meteorological Organization|website=International Cloud Atlas}}</ref>

At latitudes of [[65th parallel north|65°&nbsp;N]] or [[65th parallel south|S]], close to [[polar regions of Earth|polar regions]], cirrus clouds form, on average, only {{convert|7000|m|ft|abbr=on}} above sea level. In temperate regions, at roughly [[45th parallel north|45°&nbsp;N]] or [[45th parallel south|S]], their average altitude increases to {{convert|9500|m|ft|abbr=on}} above sea level. In [[tropics|tropical regions]], at roughly [[5th parallel north|5°&nbsp;N]] or [[5th parallel south|S]], cirrus clouds form {{convert|13500|m|ft|abbr=on}} above sea level on average. Across the globe, cirrus clouds can form anywhere from {{convert|4000|to|20000|m|ft|abbr=on}} above sea level.<ref name="D&R-973">{{harvnb|Dowling|Radke|1990|p=973}}</ref> Cirrus clouds form with a vast range of thicknesses. They can be as little as {{convert|100|m|ft|abbr=on|sigfig=2}} from top to bottom to as thick as {{convert|8000|m|ft|abbr=on|sigfig=2}}. Cirrus cloud thickness is usually somewhere between those two extremes, with an average thickness of {{convert|1500|m|ft|abbr=on}}.<ref name="D&R-977" />

The [[jet stream]], a high-level wind band, can stretch cirrus clouds long enough to cross continents.<ref name="D&R-974">{{harvnb|Dowling|Radke|1990|p=974}}</ref> [[Jet streak]]s, bands of faster-moving air in the jet stream, can create arcs of cirrus cloud hundreds of kilometers long.<ref name="cirrus-arc">{{cite web|url=https://earthobservatory.nasa.gov/images/145948/a-cirrus-arc|title=A Cirrus Arc|date=28 November 2019|publisher=National Aeronautics and Space Administration|website=NASA Earth Observatory|access-date=18 March 2022|archive-date=18 March 2022|archive-url=https://web.archive.org/web/20220318151229/https://earthobservatory.nasa.gov/images/145948/a-cirrus-arc|url-status=live}}</ref>

Cirrus cloud formation may be effected by organic [[aerosol]]s (particles produced by plants) acting as additional [[nucleation]] points for ice crystal formation.<ref>{{harvnb|Wolf|Zhang|Zawadowicz|Goodell|2020|p=1}}</ref><ref>{{Cite web|url=https://www.purdue.edu/newsroom/releases/2020/Q4/a-better-understanding-of-how-cirrus-clouds-form.html|title=A better understanding of how cirrus clouds form|date=1 October 2020|access-date=14 March 2022|last=Cziczo|first=Daniel|publisher=[[Purdue University]]|archive-date=3 May 2022|archive-url=https://web.archive.org/web/20220503184135/https://www.purdue.edu/newsroom/releases/2020/Q4/a-better-understanding-of-how-cirrus-clouds-form.html|url-status=live}}</ref> However, research suggests that cirrus clouds more commonly form on mineral dust or metallic particles rather than on organic ones.<ref name="cirrus-origins" />

=== Tropical cyclones ===
[[File:Isabel 2003-09-10 1640Z.jpg|thumb|alt=A picture showing the vast shield of cirrus clouds accompanying Hurricane Isabel in 2003|A vast shield of cirrus clouds accompanying the west side of [[Hurricane Isabel]]]]Sheets of cirrus clouds commonly fan out from the [[eye (cyclone)|eye walls]] of tropical cyclones.<ref name="cirrus-detection"/> (The eye wall is the ring of storm clouds surrounding the eye of a tropical cyclone.<ref>{{cite web|url=https://www.weather.gov/jetstream/tc_structure|title=Tropical Cyclone Structure|access-date=18 March 2022|website=NWS JetStream|publisher=National Oceanic and Atmospheric Administration|archive-date=16 November 2021|archive-url=https://web.archive.org/web/20211116033142/https://www.weather.gov/jetstream/tc_structure|url-status=live}}</ref>) A [[Central dense overcast|large shield of cirrus]] and [[cirrostratus cloud|cirrostratus]] typically accompanies the high altitude [[outflow (meteorology)|outflowing winds]] of tropical cyclones,<ref name="cirrus-detection"/> and these can make the underlying [[rain band|bands of rain]]—and sometimes even the eye—difficult to detect in satellite photographs.<ref>{{cite web|url=http://www.nrlmry.navy.mil/sat_training/tropical_cyclones/ssmi/composite/index.html|title=Tropical Cyclone SSMI – Composite Tutorial|publisher=[[United States Navy]]|access-date=18 February 2011|archive-date=4 December 2010|archive-url=https://web.archive.org/web/20101204103432/http://www.nrlmry.navy.mil/sat_training/tropical_cyclones/ssmi/composite/index.html|url-status=dead}}</ref>

=== Thunderstorms ===
[[File:Cirren von Cumulonimbus-Amboss und Cu&Sc.JPG|thumb|alt=A picture showing the cirrus clouds lancing out from the anvil of the thunderstorm, taken just before the lower mass of the cumulonimbus cloud went over the photographer|White cirrus in an anvil cloud]]
[[Thunderstorm]]s can form dense cirrus at their tops. As the cumulonimbus cloud in a thunderstorm grows vertically, the liquid water droplets freeze when the air temperature reaches the [[freezing point]].<ref name="lydolph-122">{{harvnb|Lydolph|1985|p=122}}</ref> The [[anvil cloud]] takes its shape because the [[temperature inversion]] at the tropopause prevents the warm, moist air forming the thunderstorm from rising any higher, thus creating the flat top.<ref name="G&N-212">{{harvnb|Grenci|Nese|2001|p=212}}</ref> In the tropics, these thunderstorms occasionally produce copious amounts of cirrus from their anvils.<ref>{{cite web|title=Computer-simulated Thunderstorms with Ice Clouds Reveal Insights for Next-generation Computer Models |url=http://www.pnl.gov/science/highlights/highlight.asp?id=709 |work=Atmospheric Sciences & Global Change Division Research Highlights |publisher=Pacific Northwest National Laboratory |access-date=30 January 2011 |page=42 |date=December 2009 |archive-url=https://web.archive.org/web/20110514115603/http://www.pnl.gov/science/highlights/highlight.asp?id=709 |archive-date=14 May 2011 }}</ref> High-altitude winds commonly push this dense mat out into an anvil shape that stretches [[downwind]] as much as several kilometers.<ref name="G&N-212"/>

Individual cirrus cloud formations can be the remnants of anvil clouds formed by thunderstorms. In the dissipating stage of a cumulonimbus cloud, when the normal column rising up to the anvil has evaporated or dissipated, the mat of cirrus in the anvil is all that is left.<ref name="G&N-213">{{harvnb|Grenci|Nese|2001|p=213}}</ref>

=== Contrails ===
[[Contrail]]s are an [[anthropogenic cloud|artificial type]] of cirrus cloud formed when water vapor from the exhaust of a [[jet engine]] condenses on particles, which come from either the surrounding air or the exhaust itself, and freezes, leaving behind a visible trail. The exhaust can trigger the formation of cirrus by providing [[ice nuclei]] when there is an insufficient naturally-occurring supply in the atmosphere.<ref name="McGraw-2"/> One of the [[Environmental impact of aviation|environmental impacts of aviation]] is that persistent contrails can form into large mats of cirrus,<ref name="NASA-cirrus">{{cite web|url=http://www.nasa.gov/home/hqnews/2004/apr/HQ_04140_clouds_climate.html|publisher=[[National Aeronautics and Space Administration]]|title=Clouds Caused By Aircraft Exhaust May Warm The U.S. Climate|date=27 April 2004|first1=Gretchen|last1=Cook-Anderson|first2=Chris|last2=Rink|first3=Julia|last3=Cole|access-date=24 June 2011|archive-date=18 May 2011|archive-url=https://web.archive.org/web/20110518194600/http://www.nasa.gov/home/hqnews/2004/apr/HQ_04140_clouds_climate.html|url-status=live}}</ref> and increased air traffic has been implicated as one possible cause of the increasing frequency and amount of cirrus in Earth's atmosphere.<ref name="NASA-cirrus"/><ref name="Minnis-1671">{{harvnb|Minnis|Ayers|Palikonda|Phan|2004|p=1671}}</ref>
{{clear}}

== Use in forecasting ==
{{See also|Weather forecasting|Tropical cyclone track forecasting}}
[[File:Highcloudsymbols.gif|thumb|upright=1.35|High cloud weather map symbols|left]]
Random, isolated cirrus do not have any particular significance.<ref name="audubon-447"/> A large number of cirrus clouds can be a sign of an approaching [[weather front|frontal system]] or upper air disturbance. The appearance of cirrus signals a change in weather—usually more stormy—in the near future.<ref name="WeatherBattan">{{harvnb|Battan|1974|p=74}}</ref> If the cloud is a ''[[cirrus castellanus cloud|cirrus castellanus]]'', there might be instability at the high altitude level.<ref name="audubon-447">{{harvnb|Audubon|2000|p=447}}</ref> When the clouds deepen and spread, especially when they are of the ''cirrus radiatus'' variety or ''cirrus fibratus'' species, this usually indicates an approaching weather front. If it is a warm front, the cirrus clouds spread out into cirrostratus, which then thicken and lower into [[Altocumulus cloud|altocumulus]] and [[Altostratus cloud|altostratus]]. The next set of clouds are the rain-bearing [[nimbostratus cloud]]s.<ref name="cloud-classification"/><ref name="audubon-447"/><ref name="whiteman-84">{{harvnb|Whiteman|2000|p=84}}</ref> When cirrus clouds precede a [[cold front]], [[squall line]] or [[multicellular thunderstorm]], it is because they are blown off the anvil, and the next clouds to arrive are the cumulonimbus clouds.<ref name="whiteman-84"/> Kelvin-Helmholtz waves indicate extreme wind shear at high levels.<ref name="audubon-447"/> When a jet streak creates a large arc of cirrus, weather conditions may be right for the development of [[winter storm]]s.<ref name="cirrus-arc" />

Within the tropics, 36&nbsp;hours prior to the center passage of a tropical cyclone, a veil of white cirrus clouds approaches from the direction of the cyclone.<ref>{{cite web|author=Central Pacific Hurricane Center|date=23 July 2006|url=http://www.prh.noaa.gov/cphc/pages/FAQ/Observations.php|title=Tropical Cyclone Observations|access-date=5 May 2008|publisher=[[National Oceanic and Atmospheric Administration]]|archive-url=https://web.archive.org/web/20170322035214/http://www.prh.noaa.gov/cphc/pages/FAQ/Observations.php|archive-date=22 March 2017|author-link=Central Pacific Hurricane Center}}</ref> In the mid- to late-19th century, forecasters used these cirrus veils to predict the arrival of hurricanes. In the early 1870s the president of Belén College in [[Havana]], Father [[Benito Vines|Benito Viñes]], developed the first hurricane forecasting system; he mainly used the motion of these clouds in formulating his predictions.<ref>{{harvnb|Sheets|1990|p=190}}</ref> He would observe the clouds hourly from 4:00&nbsp;am to 10:00&nbsp;pm. After accumulating enough information, Viñes began accurately predicting the paths of hurricanes; he summarized his observations in his book ''Apuntes Relativos a los Huracanes de las Antilles'', published in English as ''Practical Hints in Regard to West Indian Hurricanes''.<ref>{{cite news|url=http://www.cubanet.org/CNews/y98/mar98/13e5.htm |publisher=Cable News Network, Inc |title=Father Hurricane |access-date=22 February 2011 |date=11 March 1998 |archive-url=https://web.archive.org/web/20110725212329/http://www.cubanet.org/CNews/y98/mar98/13e5.htm |archive-date=25 July 2011 }}</ref>

== Effects on climate ==
Cirrus clouds cover up to 25% of the Earth (up to 70% in the tropics at night<ref>{{harvnb|Lolli|Campbell|Lewis|Gu|2017|loc=Section 3}}</ref>) and have a net heating effect.<ref name="Nucleation">{{harvnb|Franks|2003|pp=557–574}}</ref> When they are thin and translucent, the clouds efficiently absorb outgoing [[infrared]] radiation while only marginally reflecting the incoming sunlight.<ref name="stephens-1742">{{harvnb|Stephens|Tsay|Stackhouse|Flatau|1990|p=1742}}</ref> When cirrus clouds are {{convert|100|m|ft|abbr=on}} thick, they reflect only around 9% of the incoming sunlight, but they prevent almost 50% of the outgoing infrared radiation from escaping, thus raising the temperature of the atmosphere beneath the clouds by an average of 10&nbsp;°C (18&nbsp;°F)<ref name="liou-1191">{{harvnb|Liou|1986|p=1191}}</ref>—a process known as the [[greenhouse effect]].<ref name="earthobs-global-warming">{{cite web|url=http://earthobservatory.nasa.gov/Features/GlobalWarming/|publisher=National Aeronautics and Space Administration|title=Global Warming: Feature Articles|access-date=16 October 2012|work=Earth Observatory|date=3 June 2010|archive-date=5 May 2020|archive-url=https://web.archive.org/web/20200505194248/https://earthobservatory.nasa.gov/features/GlobalWarming|url-status=live}}</ref> Averaged worldwide, cloud formation results in a temperature loss of 5&nbsp;°C (9&nbsp;°F) at the earth's surface, mainly the result of [[stratocumulus cloud]]s.<ref name="cloud-heating">{{cite web|url=http://isccp.giss.nasa.gov/role.html|title=Cloud Climatology|work=International Satellite Cloud Climatology Program|publisher=National Aeronautics and Space Administration|access-date=12 July 2011|archive-date=30 January 2020|archive-url=https://web.archive.org/web/20200130020610/https://isccp.giss.nasa.gov/role.html|url-status=live}}</ref>

Cirrus clouds are likely becoming more common due to [[climate change]]. As their greenhouse effect is stronger than their reflection of sunlight, this would act as a [[climate change feedback|self-reinforcing feedback]].{{Sfn|Forster|Storelvmo|Armour|Collins|2021|loc=7:66, Section 7.4.2.4.2}} [[Air pollution|Metallic particles from human sources]] act as additional nucleation seeds, potentially increasing cirrus cloud cover and thus contributing further to climate change.<ref name="cirrus-origins" /> Aircraft in the upper troposphere can create [[contrail|contrail cirrus clouds]] if local weather conditions are right. These contrails contribute to climate change.<ref>{{Cite journal|last=Kärcher|first=Bernd|date=2018|title=Formation and radiative forcing of contrail cirrus|journal=Nature Communications|language=en|volume=9|issue=1|page=1824|doi=10.1038/s41467-018-04068-0|pmid=29739923 |pmc=5940853 |bibcode=2018NatCo...9.1824K |issn=2041-1723}}</ref>

[[Cirrus cloud thinning]] has been proposed as a possible [[geoengineering]] approach to reduce climate damage due to [[carbon dioxide]]. Cirrus cloud thinning would involve injecting particles into the upper troposphere to reduce the amount of cirrus clouds. The [[IPCC Sixth Assessment Report|2021 IPCC Assessment Report]] expressed low confidence in the cooling effect of cirrus cloud thinning, due to limited understanding.{{sfn|Lee|Marotzke|Bala|Cao|2021|loc=4:89, Section 4.6.3.3}}

== Cloud properties ==
[[File:Cirrus fibratus and Cirrocumulus.jpg|thumb|alt=Long, thin, straight cirrus against a blue sky on the left merging to cirrocumulus on the right|Cirrus clouds merging to cirrocumulus clouds]]

Scientists have studied the properties of cirrus using several different methods. [[Lidar]] (laser-based [[radar]]) gives highly accurate information on the cloud's altitude, length, and width. Balloon-carried [[hygrometer]]s{{efn|A hygrometer is a device used to measure humidity.}} measure the humidity of the cirrus cloud but are not accurate enough to measure the depth of the cloud. Radar units give information on the altitudes and thicknesses of cirrus clouds.<ref name="D&R-971">{{harvnb|Dowling|Radke|1990|p=971}}</ref> Another data source is satellite measurements from the [[Stratospheric Aerosol and Gas Experiment]] program. These satellites measure where [[infrared radiation]] is absorbed in the atmosphere, and if it is absorbed at cirrus altitudes, then it is assumed that there are cirrus clouds in that location.<ref name="D&R-972">{{harvnb|Dowling|Radke|1990|p=972}}</ref> [[NASA]]'s [[Moderate-Resolution Imaging Spectroradiometer]] gives information on the cirrus cloud cover by measuring reflected infrared radiation of various specific frequencies during the day. During the night, it determines cirrus cover by detecting the Earth's infrared emissions. The cloud reflects this radiation back to the ground, thus enabling satellites to see the "shadow" it casts into space.<ref name=cirrus-detection>{{cite web|title=Cirrus Cloud Detection|url=http://www.nrlmry.navy.mil/sat_training/nexsat/cirrus/NexSat_Cirrus.pdf|work=Satellite Product Tutorials|publisher=NASA (NexSat)|access-date=29 January 2011|page=2, 3, & 5|archive-date=3 April 2019|archive-url=https://web.archive.org/web/20190403015955/https://www.nrlmry.navy.mil/sat_training/nexsat/cirrus/NexSat_Cirrus.pdf}}</ref> Visual observations from aircraft or the ground provide additional information about cirrus clouds.<ref name="D&R-972"/> Particle Analysis by Laser [[Mass Spectrometry]] (PALMS){{efn|The PALMS instrument utilizes an [[Ultraviolet light|ultraviolet]] laser to vaporize aerosol particles<ref>{{cite web|url=https://airbornescience.nasa.gov/instrument/PALMS|title=Particle Analysis by Laser Mass Spectrometry (PALMS)|access-date=18 March 2022|website=NASA Airborne Science Program|publisher=National Aeronautics and Space Administration|archive-date=3 May 2022|archive-url=https://web.archive.org/web/20220503184131/https://airbornescience.nasa.gov/instrument/PALMS|url-status=live}}</ref> in a vacuum. The ionized particles are analyzed with a mass spectrometer to determine mass and composition.<ref>{{cite web|url=https://csl.noaa.gov/groups/csl2/instruments/palms/instrument.html|title=Aerosol Properties & Processes: Instruments: PALMS|access-date=18 March 2022|website=NOAA Chemical Sciences Laboratory|publisher=National Oceanic and Atmospheric Administration|archive-date=3 May 2022|archive-url=https://web.archive.org/web/20220503184130/https://csl.noaa.gov/groups/csl2/instruments/palms/instrument.html|url-status=live}}</ref>}} is used to identify the type of nucleation seeds that spawned the ice crystals in a cirrus cloud.<ref name="cirrus-origins" />

Cirrus clouds have an average ice crystal concentration of 300,000 ice crystals per 10 [[cubic metre|cubic meters]] (270,000 ice crystals per 10 [[cubic yard]]s). The concentration ranges from as low as 1 ice crystal per 10 cubic meters to as high as 100 million ice crystals per 10 cubic meters (just under 1 ice crystal per 10 cubic yards to 77 million ice crystals per 10 cubic yards), a difference of eight [[orders of magnitude]]. The size of each ice crystal is typically 0.25&nbsp;millimeters,<ref name="D&R-977">{{harvnb|Dowling|Radke|1990|p=977}}</ref> but they range from as short as 0.01&nbsp;millimeters up to several millimeters.<ref name="McGraw-1"/> The ice crystals in contrails can be much smaller than those in naturally-occurring cirrus cloud, being around 0.001&nbsp;millimeters to 0.1&nbsp;millimeters in length.<ref name="McGraw-2">{{harvnb|McGraw-Hill Editorial Staff|2005|p=2}}</ref>

In addition to forming in different sizes, the ice crystals in cirrus clouds can crystallize in different shapes: solid columns, hollow columns, plates, rosettes, and conglomerations of the various other types. The shape of the ice crystals is determined by the air temperature, [[atmospheric pressure]], and ice [[supersaturation]] (the amount by which the [[relative humidity]] exceeds 100%). Cirrus in temperate regions typically have the various ice crystal shapes separated by type. The columns and plates concentrate near the top of the cloud, whereas the rosettes and conglomerations concentrate near the base. In the northern [[Arctic]] region, cirrus clouds tend to be composed of only the columns, plates, and conglomerations, and these crystals tend to be at least four times larger than the minimum size. In [[Antarctica]], cirrus are usually composed of only columns which are much longer than normal.<ref name="McGraw-1"/>

Cirrus clouds are usually colder than {{convert|-20|C|F|abbr=on}}.<ref name="McGraw-1">{{harvnb|McGraw-Hill Editorial Staff|2005|p=1}}</ref> At temperatures above {{convert|-68|C|F}}, most cirrus clouds have relative humidities of roughly 100% (that is they are saturated).{{sfn|Krämer|Schiller|Afchine|Bauer|2009|p=3516}} Cirrus can supersaturate, with relative humidities over ice that can exceed 200%.{{sfn|Krämer|Schiller|Afchine|Bauer|2009|p=3505}}{{sfn|Krämer|Schiller|Afchine|Bauer|2009|p=3516}} Below {{convert|-68|C|F}} there are more of both undersaturated and supersaturated cirrus clouds.{{sfn|Krämer|Schiller|Afchine|Bauer|2009|p=3517}} The more supersaturated clouds are probably young cirrus.{{sfn|Krämer|Schiller|Afchine|Bauer|2009|p=3516}}

== Optical phenomena ==
[[File:CircumhorizonArcIdaho.jpg|thumb|alt=A rainbow section in the sky|Circumhorizontal arc|left]]

Cirrus clouds can produce several optical effects like [[halo (optical phenomenon)|halos]] around the Sun and Moon. Halos are caused by interaction of the light with hexagonal ice crystals present in the clouds which, depending on their shape and orientation, can result in a wide variety of white and colored rings, arcs and spots in the sky, including [[sun dog]]s,<ref name="McGraw-1" /> the [[46° halo]],<ref name="Diedenhoven-475">{{harvnb|Diedenhoven|2014|p=475}}</ref> the [[22° halo]],<ref name="Diedenhoven-475" /> and [[circumhorizontal arc]]s.<ref name="natlgeo-rainbow">{{cite news|last=Gilman|first=Victoria|title=Photo in the News: Rare "Rainbow" Spotted Over Idaho|url=http://news.nationalgeographic.com/news/2006/06/060619-rainbow-fire.html|access-date=30 January 2011|newspaper=National Geographic News|date=19 June 2006|archive-url=https://web.archive.org/web/20070107030605/http://news.nationalgeographic.com/news/2006/06/060619-rainbow-fire.html|archive-date=7 January 2007}}</ref><ref name="ucsb">{{cite web|title=Fire Rainbows |url=http://www.geog.ucsb.edu/events/department-news/618/fire-rainbows/|work=News & Events|publisher=University of the City of Santa Barbara Department of Geology|access-date=31 January 2011|date=29 August 2009|archive-url=https://web.archive.org/web/20110512173057/http://www.geog.ucsb.edu/events/department-news/618/fire-rainbows/|archive-date=12 May 2011}}</ref> Circumhorizontal arcs are only visible when the Sun rises higher than 58° above the horizon, preventing observers at higher latitudes from ever being able to see them.<ref>{{cite web|url=https://cloudatlas.wmo.int/en/circumhorizontal-arc.html|publisher=World Meteorological Organization|access-date=15 March 2022|title=Circumhorizontal arc|website=International Cloud Atlas|archive-date=3 May 2022|archive-url=https://web.archive.org/web/20220503184132/https://cloudatlas.wmo.int/en/circumhorizontal-arc.html|url-status=live}}</ref>

More rarely, cirrus clouds are capable of producing [[glory (optical phenomenon)|glories]], more commonly associated with liquid water-based clouds such as [[stratus cloud|stratus]]. A glory is a set of concentric, faintly-colored glowing rings that appear around the shadow of the observer, and are best observed from a high viewpoint or from a plane.<ref name="glory-weather.gov">{{cite web|url=http://www.weather.gov.hk/education/edu06nature/ele_glory1106_e.htm|title=The Mysterious Glory|publisher=The Hong Kong Observatory|access-date=27 June 2011|archive-date=3 April 2012|archive-url=https://web.archive.org/web/20120403033423/http://www.weather.gov.hk/education/edu06nature/ele_glory1106_e.htm|url-status=live}}</ref> Cirrus clouds only form glories when the constituent ice crystals are [[wikt:aspherical|aspherical]]; researchers suggest that the ice crystals must be between 0.009&nbsp;millimeters and 0.015&nbsp;millimeters in length for a glory to appear.<ref name="glory-1433">{{harvnb|Sassen|Arnott|Barnett|Aulenbach|1998|p=1433}}</ref>

== Relation to other clouds ==
{{See also|List of cloud types}}
[[File:Cloud types en.svg|thumb|upright=1.6|alt=A diagram showing clouds at various heights|Heights of various cloud genera including high-, mid-, and low-level clouds]]
Cirrus clouds are one of three different genera of high-level clouds, all of which are given the prefix "cirro-". The other two genera are [[cirrocumulus cloud|cirrocumulus]] and cirrostratus. High-level clouds usually form above {{convert|20000|ft|m|order=flip|abbr=on}}.<ref name="cloud-classification" /><ref name="wmo-cloud-classification">{{cite web|url=https://public-old.wmo.int/en/WorldMetDay2017/classifying-clouds|archive-url=https://web.archive.org/web/20231218182558/https://public-old.wmo.int/en/WorldMetDay2017/classifying-clouds|archive-date=18 December 2023|access-date=14 March 2022|title=Classifying clouds|date=18 January 2017|publisher=[[World Meteorological Organization]]}}</ref><ref name="H&H-340">{{harvnb|Hubbard|2000|p=340}}</ref> Cirrocumulus and cirrostratus are sometimes informally referred to as ''cirriform clouds'' because of their frequent association with cirrus.<ref>{{cite web|url=https://glossary.ametsoc.org/wiki/Cirriform|title=Cirriform – Glossary of Meteorology|access-date=23 February 2022|publisher=American Meteorological Society|archive-date=23 February 2022|archive-url=https://web.archive.org/web/20220223170359/https://glossary.ametsoc.org/wiki/Cirriform|url-status=live}}</ref>

In the intermediate range, from {{convert|6500|to|20000|ft|m|order=flip|abbr=on}},<ref name="cloud-classification" /><ref name="wmo-cloud-classification" /> are the mid-level clouds, which are given the prefix "alto-". They comprise two genera, [[altostratus cloud|altostratus]] and [[altocumulus cloud|altocumulus]]. These clouds are formed from ice crystals, supercooled water droplets, or liquid water droplets.<ref name="cloud-classification" />

Low-level clouds usually form below {{convert|6500|ft|m|order=flip|abbr=on}} and do not have a prefix.<ref name="cloud-classification" /><ref name="wmo-cloud-classification" /> The two genera that are strictly low-level are [[stratus cloud|stratus]], and [[stratocumulus cloud|stratocumulus]]. These clouds are composed of water droplets, except during winter when they are formed of [[supercooled water]] droplets or ice crystals if the temperature at cloud level is below freezing. Three additional genera usually form in the low-altitude range, but may be based at higher levels under conditions of very low humidity. They are the genera [[cumulus cloud|cumulus]], and [[cumulonimbus cloud|cumulonimbus]], and [[nimbostratus cloud|nimbostratus]]. These are sometimes classified separately as clouds of vertical development, especially when their tops are high enough to be composed of supercooled water droplets or ice crystals.<ref name="Plymouth State Meteorology">{{cite web | url=http://vortex.plymouth.edu/clouds.html/ | title=Plymouth State Meteorology Program Cloud Boutique | author=Koermer, Jim | year=2011 | access-date=2 April 2012 | publisher=[[Plymouth State University]] | archive-date=10 May 2009 | archive-url=https://web.archive.org/web/20090510231716/http://vortex.plymouth.edu/clouds.html/ }}</ref><ref name="cloud-classification" />

=== Cirrocumulus ===
{{Main|Cirrocumulus cloud}}
[[File:Cirrocumulus in Hong Kong.jpg|thumb|alt=A large field of cirrocumulus clouds in a blue sky, beginning to merge near the upper left|Large field of cirrocumulus clouds|left]]

Cirrocumulus clouds form in sheets or patches<ref name="YDN-364">{{harvnb|Miyazaki|Yoshida|Dobashi|Nishita|2001|p=364}}</ref> and do not cast shadows. They commonly appear in regular, rippling patterns<ref name="H&H-340"/> or in rows of clouds with clear areas between.<ref name="cloud-classification"/> Cirrocumulus are, like other members of the cumuliform category, formed via [[convection|convective]] processes.<ref name="parungo-251">{{harvnb|Parungo|1995|p=251}}</ref> Significant growth of these patches indicates high-altitude instability and can signal the approach of poorer weather.<ref name="common-clouds"/><ref name="audubon-448"/> The ice crystals in the bottoms of cirrocumulus clouds tend to be in the form of hexagonal cylinders. They are not solid, but instead tend to have stepped funnels coming in from the ends. Towards the top of the cloud, these crystals have a tendency to clump together.<ref name="parungo-252">{{harvnb|Parungo|1995|p=252}}</ref> These clouds do not last long, and they tend to change into cirrus because as the water vapor continues to deposit on the ice crystals, they eventually begin to fall, destroying the upward convection. The cloud then dissipates into cirrus.<ref name="parungo-254">{{harvnb|Parungo|1995|p=254}}</ref> Cirrocumulus clouds come in four species: ''stratiformis'', ''lenticularis'', ''castellanus'', and ''floccus''.<ref name="common-clouds">{{cite web|title=Common Cloud Names, Shapes, and Altitudes|publisher=Georgia Institute of Technology |url=http://nenes.eas.gatech.edu/Cloud/Clouds.pdf|access-date=12 February 2011|page=2, 10–13|archive-url=https://web.archive.org/web/20110512162814/http://nenes.eas.gatech.edu/Cloud/Clouds.pdf|archive-date=12 May 2011}}</ref> They are [[iridescence|iridescent]] when the constituent supercooled water droplets are all about the same size.<ref name="audubon-448">{{harvnb|Audubon|2000|p=448}}</ref>

=== Cirrostratus ===
{{Main|Cirrostratus cloud}}
[[File:Close Cirrostratus.jpg|thumb|alt=Milky-white cirrostratus clouds cause the sky to appear lighter and have a milky tint.|Cirrostratus cloud]]

Cirrostratus clouds can appear as a milky sheen in the sky<ref name="common-clouds"/> or as a striated sheet.<ref name="H&H-340"/> They are sometimes similar to altostratus and are distinguishable from the latter because the Sun or Moon is always clearly visible through transparent cirrostratus, in contrast to altostratus which tends to be opaque or translucent.<ref name="Day-56">{{harvnb|Day|2005|p=56}}</ref> Cirrostratus come in two species, ''fibratus'' and ''nebulosus''.<ref name="common-clouds"/> The ice crystals in these clouds vary depending upon the height in the cloud. Towards the bottom, at temperatures of around {{convert|-35|to|-45|C|F}}, the crystals tend to be long, solid, hexagonal columns. Towards the top of the cloud, at temperatures of around {{convert|-47|to|-52|C|F}}, the predominant crystal types are thick, hexagonal plates and short, solid, hexagonal columns.<ref name="parungo-254"/><ref name="parungo-256">{{harvnb|Parungo|1995|p=256}}</ref> These clouds commonly produce halos, and sometimes the halo is the only indication that such clouds are present.<ref name="ahrens-120">{{harvnb|Ahrens|2006|p=120}}</ref> They are formed by warm, moist air being lifted slowly to a very high altitude.<ref>{{harvnb|Hamilton|2007|p=24}}</ref> When a warm front approaches, cirrostratus clouds become thicker and descend forming altostratus clouds,<ref name="cloud-classification"/> and rain usually begins 12 to 24 hours later.<ref name="ahrens-120"/>

== Other planets ==
[[File:Clouds on Mars (51055621781).jpg|thumb|A composite black-and-white photograph showing cirrus clouds over the surface of [[Mars]]]]
[[File:Neptune clouds.jpg|alt=A composite black-and-white photograph showing cirrus clouds over the surface of Mars|thumb|Cirrus clouds on Neptune, captured during ''[[Voyager 2]]''<nowiki/>'s flyby]]
Cirrus clouds have been observed on several other planets. In 2008, the Martian Lander ''[[Phoenix Lander|Phoenix]]'' took a [[time-lapse]] photograph of a group of cirrus clouds moving across the [[Atmosphere of Mars|Martian sky]] using lidar.<ref name="NASA-photo">{{cite web|url=http://www.nasa.gov/mission_pages/phoenix/images/press/16145-animated.html|title=Clouds Move Across Mars Horizon|date=19 September 2008|access-date=15 April 2011|publisher=[[National Aeronautics and Space Administration]]|work=Phoenix Photographs|archive-date=2 June 2016|archive-url=https://web.archive.org/web/20160602213811/http://www.nasa.gov/mission_pages/phoenix/images/press/16145-animated.html|url-status=live}}</ref> Near the end of its mission, the Phoenix Lander detected more thin clouds close to the north pole of Mars. Over the course of several days, they thickened, lowered, and eventually began snowing. The total precipitation was only a few thousandths of a millimeter. James Whiteway from [[York University]] concluded that "precipitation is a component of the [Martian] [[hydrologic cycle]]".<ref name="MSNBC-Mars-snow">{{cite news |url=http://www.nbcnews.com/id/31713000 |title=How Martian Clouds Create Snowfall |first=Andrea |last=Thompson |newspaper=Space.com |date=2 July 2009 |publisher=[[NBC News]] |access-date=15 April 2011 |archive-date=23 September 2020 |archive-url=https://web.archive.org/web/20200923230037/http://www.nbcnews.com/id/31713000 |url-status=dead }}</ref> These clouds formed during the Martian night in two layers, one around {{convert|4000|m|ft|abbr=on}} above ground and the other at surface level. They lasted through early morning before being burned away by the Sun. The crystals in these clouds were formed at a temperature of {{convert|-65|C|F}}, and they were shaped roughly like ellipsoids 0.127&nbsp;millimeters long and 0.042&nbsp;millimeters wide.<ref>{{harvnb|Whiteway|Komguem|Dickinson|Cook|2009|pp=68–70}}</ref>

On Jupiter, cirrus clouds are composed of [[ammonia]]. When Jupiter's [[South Equatorial Belt]] disappeared, one hypothesis put forward by Glenn Orten was that a large quantity of ammonia cirrus clouds had formed above it, hiding it from view.<ref>{{cite web|url=https://science.nasa.gov/science-news/science-at-nasa/2010/20may_loststripe/|title=Big Mystery: Jupiter Loses a Stripe|date=20 May 2010|last=Phillips|first=Tony|publisher=[[National Aeronautics and Space Administration]]|work=Nasa Headline News – 2010|access-date=15 April 2011|archive-date=20 April 2011|archive-url=https://web.archive.org/web/20110420012725/http://science.nasa.gov/science-news/science-at-nasa/2010/20may_loststripe/|url-status=live}}</ref> NASA's [[Cassini probe]] detected these clouds on Saturn<ref>{{harvnb|Dougherty|Esposito|2009|page=118}}</ref> and thin water-ice cirrus on Saturn's moon [[Titan (moon)|Titan]].<ref>{{cite web|url=http://www.nasa.gov/mission_pages/cassini/whycassini/titan-clouds_prt.htm|title=Surprise Hidden in Titan's Smog: Cirrus-Like Clouds|publisher=[[National Aeronautics and Space Administration]]|date=3 February 2011|work=Mission News|access-date=16 April 2011|archive-date=16 April 2011|archive-url=https://web.archive.org/web/20110416182620/http://www.nasa.gov/mission_pages/cassini/whycassini/titan-clouds_prt.htm|url-status=live}}</ref> Cirrus clouds composed of [[methane]] ice exist on Uranus.<ref>{{cite web|title=Uranus |publisher=Scholastic |url=http://www2.scholastic.com/browse/article.jsp?id=4871 |access-date=16 April 2011 |archive-url=https://web.archive.org/web/20110902053831/http://www2.scholastic.com/browse/article.jsp?id=4871 |archive-date=2 September 2011 }}</ref> On Neptune, thin wispy clouds which could possibly be cirrus have been detected over the [[Great Dark Spot]]. As on Uranus, these are probably methane crystals.<ref>{{harvnb|Ahrens|2006|page=12}}</ref>

[[Infrared cirrus|Interstellar cirrus clouds]] are composed of tiny dust grains smaller than a [[micrometer (unit)|micrometer]] and are therefore not true cirrus clouds, which are composed of frozen crystals.<ref name="bluebook_c1">{{cite book |author=Planck Science Team|title=Planck: The Scientific Programme (''Blue Book'') |id=ESA-SCI (2005)-1 V2 |pages=123–124 |publisher=European Space Agency |url=http://www.rssd.esa.int/SA/PLANCK/docs/Bluebook-ESA-SCI(2005)1_V2.pdf |year=2005|archive-url=https://web.archive.org/web/20131031065018/http://www.rssd.esa.int/SA/PLANCK/docs/Bluebook-ESA-SCI(2005)1_V2.pdf |access-date=8 July 2009|archive-date=31 October 2013 }}</ref> They range from a few [[light year]]s to dozens of light years across. While they are not technically cirrus clouds, the dust clouds are referred to as "cirrus" because of their similarity to the clouds on Earth. They emit infrared radiation, similar to the way cirrus clouds on Earth reflect heat being radiated out into space.<ref>{{harvnb|Koupelis|2010|page=368}}</ref>
{{clear}}

== Notes ==
{{Notelist}}

== References ==
'''Footnotes'''
{{Reflist|30em}}

'''Bibliography'''
{{Refbegin|30em}}
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|publisher=In Press
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|access-date=19 February 2022
|archive-date=1 February 2022
|archive-url=https://web.archive.org/web/20220201061233/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_07.pdf
|url-status=live
}} <!--Forster-->
*{{cite journal |last1=Franks |first1=Felix |title=Nucleation of ice and its management in ecosystems |journal=Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences |date=15 March 2003 |volume=361 |issue=1804 |pages=557-74; discussion 574 |doi=10.1098/rsta.2002.1141 |pmid=12662454 |bibcode=2003RSPTA.361..557F |s2cid=25606767}} <!-- Franks -->
*{{cite journal|title=Cirrus Cloud Properties as Seen by the CALIPSO Satellite and ECHAM-HAM Global Climate Model|last1=Gasparini|first1=B|last2=Meyer|first2=A|last3=Neubauer|first3=D|last4=Münch|first4=S|last5=Lohmann|first5=U|journal=Journal of Climate|volume=31|issue=5|publisher=American Meteorological Society|date=1 March 2018|doi=10.1175/JCLI-D-16-0608.1|pages=1983–2003|bibcode=2018JCli...31.1983G|s2cid=134648921 |doi-access=free}} <!-- Gasparini -->
*{{cite book|title=A World of Weather: Fundamentals of Meteorology: A Text / Laboratory Manual|date=August 2001|publisher=Kendall/Hunt Publishing Company|isbn=978-0-7872-7716-1|oclc=51160155|url=https://books.google.com/books?id=oh8lqM5obuYC&pg=PA212|first1=Lee M.|last1=Grenci|first2=Jon M.|last2=Nese|edition=3rd}} <!-- Grenci -->
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*{{cite book|last1=Hubbard|first1=Richard Keith|title=Boater's Bowditch: The Small Craft American Practical Navigator|chapter-url=https://books.google.com/books?id=nfWSxRr8VP4C&pg=PA340|edition=2nd|date=5 May 2000|publisher=International Marine/Ragged Mountain Press|isbn=978-0-07-136136-1|chapter=Glossary}} <!-- Hubbard -->
*{{cite book|url=https://books.google.com/books?id=GVlpKZ67DscC&pg=PA368|title=In Quest of the Universe|first=Theo|last=Koupelis|oclc=489012016|isbn=978-0-7637-6858-4|date=February 2010|edition=6th|publisher=Jones & Bartlett Publishers}} <!-- Koupelis -->
*{{cite journal |vauthors=Krämer M, Schiller C, Afchine A, Bauer R, Gensch I, Mangold A, Schlicht S, Spelten N, Sitnikov N, Borrmann S, de Reus M, Spichtinger P |title=Ice Supersaturations and Cirrus Cloud Crystal Numbers |date=June 2009 |journal=Atmospheric Chemistry and Physics |volume=9 |issue=11 |pages=3505–3522 |doi=10.5194/acp-9-3505-2009 |bibcode=2009ACP.....9.3505K |url=https://acp.copernicus.org/articles/9/3505/2009/acp-9-3505-2009.pdf |access-date=24 February 2022 |archive-date=19 January 2022 |archive-url=https://web.archive.org/web/20220119024031/https://acp.copernicus.org/articles/9/3505/2009/acp-9-3505-2009.pdf |url-status=live |doi-access=free }} <!-- Kramer et al -->
*{{Cite book
 |chapter         = Chapter 4: Future global climate: scenario-based projections and near-term information
 |chapter-url     = https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_04.pdf
 |last1           = Lee
 |first1          = June-Yi
 |last2           = Marotzke
 |first2          = Jochem
 |last3           = Bala
 |first3          = Govindasamy
 |last4           = Cao
 |first4          = Cao
 |last5           = Corti
 |first5          = Susanna
 |display-authors = 4
 |title           = Climate Change 2021: The Physical Science Basis
 |year            = 2021
 |access-date     = 19 February 2022
 |archive-date    = 5 September 2021
 |archive-url     = https://web.archive.org/web/20210905113907/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_04.pdf
 |url-status      = live
}} <!--Lee-->
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*{{cite journal |doi=10.1364/AO.37.001427 |title=Can Cirrus Clouds Produce Glories? |journal=Applied Optics |date=March 1998 |volume=37 |issue=9 |url=http://www.dri.edu/People/pat/webWPA/pdfdocs/CirrusGlory.pdf |access-date=29 January 2011 |bibcode=1998ApOpt..37.1427S |last1=Sassen |first1=Kenneth |last2=Arnott |first2=W. Patrick |last3=Barnett |first3=Jennifer M. |last4=Aulenbach |first4=Steve |pages=1427–1433 |oclc=264468338 |pmid=18268731 |archive-url=https://web.archive.org/web/20040621174730/http://www.dri.edu/People/pat/webWPA/pdfdocs/CirrusGlory.pdf |archive-date=21 June 2004 |citeseerx=10.1.1.21.1512 }} <!-- Sassen -->
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*{{cite journal |last1=Wolf |first1=Martin J. |last2=Zhang |first2=Yue |last3=Zawadowicz |first3=Maria A. |last4=Goodell |first4=Megan |last5=Froyd |first5=Karl |last6=Freney |first6=Evelyn |last7=Sellegri |first7=Karine |last8=Rösch |first8=Michael |last9=Cui |first9=Tianqu |last10=Winter |first10=Margaux |last11=Lacher |first11=Larissa |last12=Axisa |first12=Duncan |last13=DeMott |first13=Paul J. |last14=Levin |first14=Ezra J. T. |last15=Gute |first15=Ellen |last16=Abbatt |first16=Jonathan |last17=Koss |first17=Abigail |last18=Kroll |first18=Jesse H. |last19=Surratt |first19=Jason D. |last20=Cziczo |first20=Daniel J. |title=A biogenic secondary organic aerosol source of cirrus ice nucleating particles |journal=Nature Communications |date=1 October 2020 |volume=11 |issue=1 |page=4834 |doi=10.1038/s41467-020-18424-6 |pmid=33004794 |pmc=7529764 |bibcode=2020NatCo..11.4834W }} <!-- Wolf et al -->
{{Refend}}

{{Commons category|Cirrus clouds}}

{{portalbar|Weather}}
{{Cloud types}}
{{Authority control}}

[[Category:Cirrus| ]]
[[Category:Cloud types]]