Editing Katabatic wind

{{Short description|Downslope wind due to a high-density air}}
[[File:מכתש רמון - גלישת עננים (cropped).jpg|thumb|upright=1.7|Plateau-cooled air falls into the [[Makhtesh Ramon]], traced by [[radiation fog]], just after dawn. Radiative cooling of the desert highlands chills the air, making it [[unstable stratification|more dense]] than the air over the lowlands. Cooler air can also [[relative humidity|hold less water vapour]]; it condenses out as tiny fog droplets, which re-evaporate as the air warms. Here, the falling air is warming [[adiabatically]], and so the fog re-evaporates as it falls.{{citation needed|date=August 2024}}]]
[[File:Vent catabatique - Catabatic Wind.jpg|thumb|upright=1.7|Katabatic wind in Antarctica]]

A '''katabatic wind''' (named {{etymology|grc|''{{wikt-lang|grc|κατάβασις}}'' ({{grc-transl|[[katabasis|κατάβασις]]}})|descent}}) is a downslope wind caused by the flow of an elevated, high-density air mass into a lower-density air mass below under the force of gravity. The spelling '''catabatic'''<ref>
{{cite book
| title = The NASA Scope and Subject Category Guide
| url = https://books.google.com/books?id=IMLZAAAAMAAJ
| series = NASA SP
| volume = 7603
| publisher = National Aeronautics and Space Administration, Scientific and Technical Information Office, Center for Aerospace Information
| date = 2000
| page = 71
| access-date = 2018-01-17
| quote = Katabatic winds (also catabatic)
}}
</ref> is also used. Since air density is strongly dependent on temperature, the high-density air mass is usually cooler, and the katabatic winds are relatively cool or cold.

Examples of katabatic winds include the downslope [[Mountain breeze and valley breeze|valley and mountain breezes]], the [[piteraq]] winds of Greenland, the [[Bora (wind)|Bora]] in the [[Adriatic Sea|Adriatic]],<ref>{{Cite journal |last1=Grisogono |first1=Branko |last2=BelušIć |first2=Danijel |date=January 2009 |title=A review of recent advances in understanding the meso- and microscale properties of the severe Bora wind |url=http://tellusa.net/index.php/tellusa/article/view/15531 |journal=Tellus A |language=en |volume=61 |issue=1 |pages=1–16 |doi=10.1111/j.1600-0870.2008.00369.x|bibcode=2009TellA..61....1G |url-access=subscription }}</ref> the [[Bohemian Wind]] or ''Böhmwind'' in the [[Ore Mountains]], the [[Santa Ana wind|Santa Ana winds]] in [[southern California]],  the [[oroshi]] in [[Japan]], or "the Barber" in [[New Zealand]].<ref>{{Cite web |last1=Wright |first1=Les |last2=Taonga |first2=New Zealand Ministry for Culture and Heritage Te Manatu |title='The barber' |url=https://teara.govt.nz/en/photograph/21007/the-barber |access-date=2024-12-22 |website=teara.govt.nz |language=en}}</ref>

Not all downslope winds are katabatic. For instance, winds such as the [[Foehn wind|föhn]] and [[Chinook wind|chinook]] are [[rain shadow]] winds where air driven upslope on the [[Windward and leeward|windward]] side of a mountain range drops its moisture and descends [[Windward and leeward|leeward]] drier and warmer. 

== Mechanism ==
[[File:Katabatic-wind hg.png|thumb|Sketch of the generation of katabatic winds in Antarctica]]
A katabatic wind originates from the difference of density of two air masses located above a slope. This density difference usually comes from temperature difference, even if humidity may also play a role. Schematically katabatic winds can be divided into two types for which the mechanisms are slightly different: the katabatic winds due to radiative cooling (the most common) and the [[Fall wind|fall winds]]. 

In the first case, the slope surface cools down radiatively after sunset, which cools down the air near the slope. This cooler air layer then flows down in the valley. This type of katabatic is very often observed during the night in the mountains. The term katabatic actually often refer to this type of wind.<ref>{{Cite journal |last1=Poulos |first1=Greg |last2=Zhong |first2=Shiyuan (Sharon) |date=November 2008 |title=An Observational History of Small-Scale Katabatic Winds in Mid-Latitudes |url=https://compass.onlinelibrary.wiley.com/doi/10.1111/j.1749-8198.2008.00166.x |journal=Geography Compass |language=en |volume=2 |issue=6 |pages=1798–1821 |doi=10.1111/j.1749-8198.2008.00166.x |bibcode=2008GComp...2.1798P |issn=1749-8198|url-access=subscription }}</ref>

In contrast, fall wind do not come from radiative cooling of the air, but rather from the [[advection]] of a relatively cold air mass to the top of a slope.<ref>{{Cite web |title=fall wind |url=https://www.oxfordreference.com/display/10.1093/oi/authority.20110803095809391 |access-date=2024-12-22 |website=Oxford Reference |language=en }}</ref><ref>{{Cite web |title=Fall wind - Glossary of Meteorology |url=https://glossary.ametsoc.org/wiki/Fall_wind |archive-url=https://web.archive.org/web/20220819172311/https://glossary.ametsoc.org/wiki/Fall_wind |archive-date=2022-08-19 |access-date=2024-12-22 |website=glossary.ametsoc.org |language=en |url-status=live }}</ref> This cold air mass can come from the arrival of a cold front (see [[Bora (wind)|Bora]]),<ref>{{Cite web |last=Stull |first=Roland |date=2020-03-31 |title=17.10: Downslope Winds |url=https://geo.libretexts.org/Bookshelves/Meteorology_and_Climate_Science/Practical_Meteorology_(Stull)/17:_Regional_Winds/17.10:_Downslope_Winds |access-date=2024-12-22 |website=Geosciences LibreTexts |language=en}}</ref> or from the advection of cool marine air by a sea-breeze.<ref name=":0">{{Cite journal |last1=Lunel |first1=Tanguy |last2=Jimenez |first2=Maria Antonia |last3=Cuxart |first3=Joan |last4=Martinez-Villagrasa |first4=Daniel |last5=Boone |first5=Aaron |last6=Le Moigne |first6=Patrick |date=2024-07-05 |title=The marinada fall wind in the eastern Ebro sub-basin: physical mechanisms and role of the sea, orography and irrigation |url=https://acp.copernicus.org/articles/24/7637/2024/ |journal=Atmospheric Chemistry and Physics |language=en |volume=24 |issue=13 |pages=7637–7666 |doi=10.5194/acp-24-7637-2024 |doi-access=free |bibcode=2024ACP....24.7637L |issn=1680-7324}}</ref>

== Impacts ==
[[File:Antarctic shelf ice hg.png|thumb|Coastal [[polynya]]s are produced in the Antarctic by katabatic winds]]
<!-- [[File:Sea ice by fruchtzwerg's world.jpg|thumb|Katabatic wind spilling off an ice shelf]]-->
Katabatic winds are for example found blowing out from the large and elevated ice sheets of [[Antarctica]] and [[Greenland]].  The buildup of high density cold air over the ice sheets and the elevation of the ice sheets brings into play enormous gravitational energy. Where these winds are concentrated into restricted areas in the coastal valleys, the winds blow well over hurricane force,<ref>[http://shl.stanford.edu:3455/southpole/577 Climate: The South Pole] {{webarchive|url=https://web.archive.org/web/20080918055013/http://shl.stanford.edu:3455/SouthPole/577 |date=2008-09-18 }} [http://shl.stanford.edu:3455/admin/directory.html Stanford Humanities Lab]  {{webarchive|url=https://archive.today/20060912022451/http://shl.stanford.edu:3455/admin/directory.html |date=2006-09-12 }}, Retrieved 2008-10-01</ref> reaching around {{convert|160|kn|km/h mph|abbr=on}}.<ref>Trewby, M. (Ed., 2002): ''Antarctica. An encyclopedia from Abbott Ice Shelf to Zooplankton'' Firefly Books Ltd. {{ISBN|1-55297-590-8}}</ref>  In Greenland these winds are called [[piteraq]] and are most intense whenever a low pressure area approaches the coast.

In a few regions of continental Antarctica the snow is scoured away by the force of the katabatic winds, leading to "dry valleys" (or "[[Antarctic oasis|Antarctic oases]]") such as the [[McMurdo Dry Valleys]]. Since the katabatic winds are descending, they tend to have a low relative humidity, which [[Desiccation|desiccates]] the region. Other regions may have a similar but lesser effect, leading to [[Blue-ice area|"blue ice" areas]] where the snow is removed and the surface ice [[Sublimation (phase transition)|sublimates]], but is replenished by glacier flow from upstream.

In the Fuegian Archipelago ([[Tierra del Fuego]]) in South America as well as in Alaska in North America, a wind known as a [[williwaw]] is a particular danger to harboring vessels. Williwaws originate in the snow and ice fields of the coastal mountains, and they can be faster than {{convert|120|kn|km/h mph|abbr=on}}.<ref>[http://www.weatheronline.co.uk/reports/wind/The-Williwaw.htm Williwaw] ''weatheronline.co.uk''. Accessed 2013-04-29.</ref>

In California, strong katabatic wind events have been responsible for the explosive growth of many wildfires, including the 2018 [[Camp Fire (2018)|Camp Fire]] and the 2020 [[North Complex fire|North Complex]].

In [[Catalonia]], the [[Marinada (wind)|Marinada]] is a fall wind that relieves from the heat inhabitants of the [[Urgell]] region during summer.<ref name=":0" />

== See also ==
* [[Anabatic wind]]
* [[Bora (wind)]]
* [[Foehn wind]]
* [[Piteraq]]
* [[Valley exit jet]]

== References ==
{{Reflist}}

== Further reading ==
*{{cite journal |last1=Bromwich |first1=David H. |title=Satellite Analyses of Antarctic Katabatic Wind Behavior |journal=Bulletin of the American Meteorological Society |volume=70 |issue=7 |year=1989 |pages=738–49 |doi=10.1175/1520-0477(1989)070<0738:SAOAKW>2.0.CO;2 |bibcode=1989BAMS...70..738B |doi-access=free }}
*{{cite journal |last1=Bromwich |first1=David H. |title=An Extraordinary Katabatic Wind Regime at Terra Nova Bay, Antarctica |journal=Monthly Weather Review |volume=117 |issue=3 |year=1989 |pages=688–95 |doi=10.1175/1520-0493(1989)117<0688:AEKWRA>2.0.CO;2 |bibcode=1989MWRv..117..688B |doi-access=free }}
*Giles, Bill. [http://www.bbc.co.uk/weather/features/az/alphabet31.shtml Weather A-Z - Katabatic Winds By Bill Giles OBE], BBC, Retrieved 2008-10-14
*McKnight, TL & Hess, Darrel (2000). Katabatic Winds. In ''Physical Geography: A Landscape Appreciation'', pp.&nbsp;131–2. Upper Saddle River, NJ: Prentice Hall. {{ISBN|0-13-020263-0}}
*{{cite journal |last1=Parish |first1=Thomas R. |last2=Bromwich |first2=David H. |title=Continental-Scale Simulation of the Antarctic Katabatic Wind Regime |journal=Journal of Climate |volume=4 |issue=2 |year=1991 |pages=135–46 |doi=10.1175/1520-0442(1991)004<0135:CSSOTA>2.0.CO;2 |bibcode=1991JCli....4..135P |doi-access=free }}

== External links ==
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[[Category:Wind]]
[[Category:Climate of Antarctica]]
[[Category:Climate of Greenland]]