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{{Short description|Type of dry down-slope wind occurring near mountains}}
{{Short description|Type of dry down-slope wind occurring near mountains}}
{{Redirect|Föhn|the antiaircraft rocket|Henschel Hs 297}}
{{Redirect|Föhn|the antiaircraft rocket|Henschel Hs 297}}
[[File:Foehn effect mechanisms.png|thumb|270px|The causes of the Foehn effect in the lee of mountains. Adapted from <ref name="The Causes of Foehn Warming in the">{{cite journal|last1=Elvidge|first1=Andrew D.|last2=Renfrew|first2=Ian A.|title=The Causes of Foehn Warming in the Lee of Mountains|journal=Bulletin of the American Meteorological Society|date=14 May 2015|volume=97|issue=3|pages=455–466|doi=10.1175/bams-d-14-00194.1|ref=4|bibcode=2016BAMS...97..455E|doi-access=free}}</ref>.]]
[[File:Foehn effect mechanisms.png|thumb|270px|The causes of the Foehn effect in the lee of mountains (adapted from: <ref name="The Causes of Foehn Warming in the">{{cite journal|last1=Elvidge|first1=Andrew D.|last2=Renfrew|first2=Ian A.|title=The Causes of Foehn Warming in the Lee of Mountains|journal=Bulletin of the American Meteorological Society|date=14 May 2015|volume=97|issue=3|pages=455–466|doi=10.1175/bams-d-14-00194.1|ref=4|bibcode=2016BAMS...97..455E|doi-access=free}}</ref>)]]
[[File:Cumbre Nueva 2014-05.JPG|thumb|260px|Dissolving [[Föhn cloud]]s over [[Cumbre Nueva]] (1400 m), [[La Palma]]]]
[[File:Cumbre Nueva 2014-05.JPG|thumb|260px|Dissolving [[Föhn cloud]]s over [[Cumbre Nueva]], [[La Palma]], at an elevation of {{cvt|1,400|m|ft}}]]
A '''Foehn''' or '''Föhn''' ({{IPAc-en|UK|f|ɜː|n}}, {{IPAc-en|US|f|eɪ|n}},<ref>{{cite EPD|18}}</ref><ref>{{cite LPD|3}}</ref> {{IPAc-en|usalso|f|ʌ|n|,_|f|ɜːr|n}}<ref>{{cite DPCE|2}}</ref><ref>{{cite Merriam-Webster|foehn|access-date=2022-03-17}}</ref>), is a type of dry, relatively warm, downslope wind that occurs in the [[leeward|lee]] (downwind side) of a mountain range.
It is a [[rain shadow]] wind that results from the subsequent [[adiabatic]] warming of air that has dropped most of its moisture on windward slopes (see [[orographic lift]]). As a consequence of the different adiabatic [[lapse rate]]s of moist and dry air, the air on the leeward slopes becomes warmer than equivalent elevations on the [[windward]] slopes.


A '''Foehn''', or '''Föhn''' ({{IPAc-en|UK|f|ɜː|n}}, {{IPAc-en|US|f|eɪ|n}} {{respell|fayn}},<ref>{{cite EPD|18}}</ref><ref>{{cite LPD|3}}</ref> {{IPAc-en|usalso|f|ʌ|n|,_|f|ɜːr|n}} {{respell|fu(r)n}}<ref>{{cite DPCE|2}}</ref><ref>{{cite Merriam-Webster|foehn|access-date=2022-03-17}}</ref>), is a type of dry, relatively warm [[katabatic wind|downslope wind]] in the [[leeward|lee]] of a [[mountain range]]. It is a [[rain shadow]] wind that results from the subsequent [[adiabatic]] warming of air that has dropped most of its moisture on [[windward and leeward|windward]] slopes (see [[orographic lift]]). As a consequence of the different adiabatic [[lapse rate]]s of moist and dry air, the air on the leeward slopes becomes warmer than equivalent [[elevation]]s on the windward slopes.
Foehn winds can raise [[temperature]]s by as much as 14&nbsp;°C (25&nbsp;°F)<ref name="NOAA-SD">{{cite web|title=South Dakota Weather History and Trivia for January |url=http://www.crh.noaa.gov/fsd/?n=fsdtrivia01 |publisher=National Weather Service Weather Forecast Office |date=February 8, 2006 |at=See January 22 entry}}</ref> in just a matter of hours. Switzerland, southern Germany and Austria have a warmer climate due to the Foehn, as moist winds off the Mediterranean Sea blow over the [[Alps]].

Foehn winds can raise [[atmospheric temperature|temperatures]] by as much as {{cvt|14|C-change}}<ref name="NOAA-SD">{{cite web |title=South Dakota Weather History and Trivia for January |url=https://crh.noaa.gov/fsd/?n=fsdtrivia01 |publisher=[[National Weather Service]] [[list of National Weather Service Weather forecast offices|Weather Forecast Office]] |date=February 8, 2006 |at=See January 22 entry}}</ref> in just a matter of hours. Switzerland, southern Germany, and Austria have a warmer climate due to the Foehn, as moist winds off the [[Mediterranean Sea]] blow over the [[Alps]].


==Etymology==
==Etymology==
The name ''Foehn'' ({{lang-de|Föhn}}, {{IPA-de|ˈføːn|pron}}) arose in the [[Alps|Alpine]] region. Originating from Latin ''(ventus) favonius'', a mild west wind of which [[Anemoi|Favonius]] was the Roman personification<ref>''Concise Oxford Dictionary'', 10th edition, Oxford University Press, entry ''föhn''.</ref> and probably transmitted by {{lang-rm|favuogn}} or just ''fuogn'', the term was adopted as {{lang-goh|phōnno}}. In the Southern Alps, the phenomenon is known as ''Föhn'' but also {{lang-it|favonio}} and ''fen'' in [[Serbo-Croatian language|Serbo-Croatian]] and [[Slovene language|Slovene]]. The German word ''Föhn'' (pronounced the same way) also means "hairdryer", while the word ''Fön'' is a [[genericized trademark]] today owned by [[AEG]].<ref>{{cite web|title=22. Januar 2009 – Vor 100 Jahren: "Fön" ins Markenregister eingetragen|periodical=WDR.de|url=https://www1.wdr.de/stichtag/stichtag4002.html|access-date=2019-12-21|date=2009-01-22}}</ref> The form ''phon'' is used in [[Romandy|French-speaking parts of Switzerland]] as well as in [[Italy]].
The name ''Foehn'' ({{langx|de|Föhn}}, {{IPA|de|ˈføːn|pron}}) arose in the [[Alps|Alpine]] region. Originating from Latin {{lang|la|(ventus) favonius}}, a mild west wind of which [[Zephyrus|Favonius]] was the Roman personification<ref>''Concise Oxford Dictionary'', 10th edition, Oxford University Press, entry ''föhn''.</ref> and probably transmitted by {{langx|rm|favuogn}} or just {{lang|rm|fuogn}}, the term was adopted as {{langx|goh|phōnno}}. In the Southern Alps, the phenomenon is known as {{lang|de|Föhn}} but also {{langx|it|favonio}} and {{lang|sh|fen}} in [[Serbo-Croatian language|Serbo-Croatian]] and [[Slovene language|Slovene]]. The German word {{lang|de|Föhn}} (pronounced the same way) also means 'hairdryer', while the word {{lang|de|Fön}} is a [[genericized trademark]] today owned by [[AEG (German company)|AEG]].<ref>{{cite web|title=22. Januar 2009 – Vor 100 Jahren: "Fön" ins Markenregister eingetragen|periodical=WDR.de|url=https://www1.wdr.de/stichtag/stichtag4002.html|access-date=2019-12-21|date=2009-01-22}}</ref> The form ''phon'' is used in [[Romandy|French-speaking parts of Switzerland]] as well as in [[Italy]].


The name "Föhn" was originally used to refer to the south wind which blows during the winter months and brings thaw conditions to the northern side of the [[Alps]]. Because Föhn later became a generic term that was extended to other mountain ranges around the world that experience similar phenomena, the name "[[Alpine föhn]]" (''Alpenföhn'') was coined for the Föhns of the Alpine region.<ref name="Brockhaus">''Der Brockhaus. Wetter und Klima.'' Seite 101, Brockhaus, Leipzig/Mannheim, 2009, {{ISBN|978-3-7653-3381-1}}</ref>
The name {{lang|de|Föhn}} was originally used to refer to the south wind which blows during the winter months and brings thaw conditions to the northern side of the [[Alps]]. Because Föhn later became a generic term that was extended to other mountain ranges around the world that experience similar phenomena, the name "[[Alpine föhn]]" ({{lang|de|Alpenföhn}}) was coined for the Föhns of the Alpine region.<ref name="Brockhaus">''Der Brockhaus. Wetter und Klima.'' Seite 101, Brockhaus, Leipzig/Mannheim, 2009, {{ISBN|978-3-7653-3381-1}}</ref>


== Causes ==
== Causes ==
[[File:Val cenis stausee.jpg|thumb|upright=2|The warm moist air from northern Italy is blocked on the [[windward]] side, loses much of its water vapour content, and descends on the French plateau and valley of the Mont-Cenis range in the [[Maurienne valley]]]]
[[File:Val cenis stausee.jpg|thumb|upright=1.5|The warm moist air from northern Italy is blocked on the [[windward]] side, loses much of its water vapour content, and descends on the French plateau and valley of the Mont-Cenis range in the [[Maurienne valley]].]]
There are four known causes of the Foehn warming and drying effect.<ref name="The Causes of Foehn Warming in the"/> These mechanisms often act together, with their contributions varying depending on the size and shape of the mountain barrier and on the meteorological conditions, such as the upstream wind speed, temperature and humidity.
There are four known causes of the Foehn warming and drying effect.<ref name="The Causes of Foehn Warming in the"/> These mechanisms often act together, with their contributions varying depending on the size and shape of the mountain barrier and on the meteorological conditions, such as the upstream wind speed, temperature and humidity.


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When winds blow over elevated terrain, air forced upwards expands and cools due to the decrease in pressure with height. Since colder air can hold less water vapour, moisture condenses to form clouds and precipitates as rain or snow on the mountain's upwind slopes. The change of state from vapour to liquid water releases [[latent heat]] energy which heats the air, partially countering the cooling that occurs as the air rises. The subsequent removal of moisture as precipitation renders this heat gain by the air irreversible, leading to the warm, dry, Foehn conditions as the air descends in the mountain's lee. This mechanism has become a popular textbook example of atmospheric thermodynamics. However, the common occurrence of 'dry' Foehn events, where there is no precipitation, implies there must be other mechanisms.
When winds blow over elevated terrain, air forced upwards expands and cools due to the decrease in pressure with height. Since colder air can hold less water vapour, moisture condenses to form clouds and precipitates as rain or snow on the mountain's upwind slopes. The change of state from vapour to liquid water releases [[latent heat]] energy which heats the air, partially countering the cooling that occurs as the air rises. The subsequent removal of moisture as precipitation renders this heat gain by the air irreversible, leading to the warm, dry, Foehn conditions as the air descends in the mountain's lee. This mechanism has become a popular textbook example of atmospheric thermodynamics. However, the common occurrence of 'dry' Foehn events, where there is no precipitation, implies there must be other mechanisms.


[[File:Foehn rotor cloud.jpg|thumb|Rotor cloud revealing overturning and turbulence above the lee slopes of the Antarctic Peninsula during a westerly Foehn event.]]
[[File:Foehn rotor cloud.jpg|thumb|Rotor cloud revealing overturning and turbulence above the lee slopes of the Antarctic Peninsula during a westerly Foehn event]]


===Isentropic draw-down===
===Isentropic draw-down===
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== Purported physiological effects ==
== Purported physiological effects ==
Anecdotally, residents in areas of frequent Foehn winds have reported experiencing a variety of illnesses ranging from [[migraine]]s to [[psychosis]]. The first clinical review of these effects was published by the Austrian physician Anton Czermak in the 19th century.<ref>{{cite journal | last1 = Giannini | first1 = AJ | last2 = Malone | first2 = DA | last3 = Piotrowski | first3 = TA | title = The serotonin irritation syndrome – a new clinical entity? | journal = The Journal of Clinical Psychiatry | volume = 47 | issue = 1 | pages = 22–25 | year = 1986 | pmid = 2416736 }}</ref> A study by the [[Ludwig-Maximilians-Universität München]] found that [[suicide]] and accidents increased by 10 percent during Foehn winds in Central Europe.{{citation needed|date=May 2009}} The causation of ''[[Föhnkrankheit]]'' (English: Foehn-sickness) is unproven. Labels for preparations of aspirin combined with [[caffeine]], [[codeine]] and the like will sometimes include ''Föhnkrankheit'' amongst the indications.{{Citation needed|date=February 2013}}<ref>See the documentary: Snow Eater (the English translation of Canadian First Nations word phonetically pronounced chinook).
Anecdotally, residents in areas of frequent Foehn winds have reported experiencing a variety of illnesses ranging from [[migraine]]s to [[psychosis]]. The first clinical review of these effects was published by the Austrian physician Anton Czermak in the 19th century.<ref>{{cite journal | last1 = Giannini | first1 = AJ | last2 = Malone | first2 = DA | last3 = Piotrowski | first3 = TA | title = The serotonin irritation syndrome – a new clinical entity? | journal = The Journal of Clinical Psychiatry | volume = 47 | issue = 1 | pages = 22–25 | year = 1986 | pmid = 2416736 }}</ref> A study by the [[Ludwig-Maximilians-Universität München]] found that [[suicide]] and accidents increased by 10 percent during Foehn winds in Central Europe.{{citation needed|date=May 2009}} The causation of ''[[Föhnkrankheit]]'' (English: Foehn-sickness) is unproven. Labels for preparations of aspirin combined with [[caffeine]], [[codeine]] and the like will sometimes include ''Föhnkrankheit'' amongst the indications.{{Citation needed|date=February 2013}}<ref>See the documentary: Snow Eater (the English translation of Canadian First Nations word phonetically pronounced chinook).
[http://www.telefilm.ca/en/catalogues/production/snow-eater telefilm.ca] {{webarchive|url=https://web.archive.org/web/20131017040732/http://www.telefilm.ca/en/catalogues/production/snow-eater |date=2013-10-17 }}.</ref> Evidence for effects from [[Chinook wind]]s remain anecdotal.
[http://www.telefilm.ca/en/catalogues/production/snow-eater telefilm.ca] {{webarchive|url=https://web.archive.org/web/20131017040732/http://www.telefilm.ca/en/catalogues/production/snow-eater |date=2013-10-17 }}.</ref> Evidence for effects from [[Chinook wind]]s remains anecdotal, as it does for New Zealand's [[Nor'west arch|Nor'wester]].<ref>Brook, K., "[https://www.canterbury.ac.nz/news/2014/grumpy-norwest-winds-.html Grumpy nor'west winds]," [[University of Canterbury]], 2 December 2014. Retrieved 22 November 2023.</ref>


In some regions, Foehn winds are associated with causing circulatory problems, headaches, or similar ailments.<ref name="tuller">{{cite journal|last1=Tuller|first1=Stanton E.|title=The Effects of a Foehn Wind on Human Thermal Exchange: The Canterbury Nor'wester|journal=New Zealand Geographer|date=April 1980|volume=36|issue=1|pages=11–19|doi=10.1111/j.1745-7939.1980.tb01919.x}}</ref> Researchers have found, however, the Foehn wind's warm temperature to be beneficial to humans in most situations, and have theorised that the reported negative effects may be a result of secondary factors, such as changes in the electrical field or in the ion state of the atmosphere, the wind's relatively low humidity, or the generally unpleasant sensation of being in an environment with strong and gusty winds.<ref name="tuller"/>
In some regions, Foehn winds are associated with causing circulatory problems, headaches, or similar ailments.<ref name="tuller">{{cite journal|last1=Tuller|first1=Stanton E.|title=The Effects of a Foehn Wind on Human Thermal Exchange: The Canterbury Nor'wester|journal=New Zealand Geographer|date=April 1980|volume=36|issue=1|pages=11–19|doi=10.1111/j.1745-7939.1980.tb01919.x|bibcode=1980NZGeo..36...11T }}</ref> Researchers have found, however, the Foehn wind's warm temperature to be beneficial to humans in most situations, and have theorised that the reported negative effects may be a result of secondary factors, such as changes in the electrical field or in the ion state of the atmosphere, the wind's relatively low humidity, or the generally unpleasant sensation of being in an environment with strong and gusty winds.<ref name="tuller"/>


== Local examples ==
== Local examples ==
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*The [[Brookings effect|Brookings Effect]] on the southwestern coast of Oregon, also known as the Chetco Effect.
*The [[Brookings effect|Brookings Effect]] on the southwestern coast of Oregon, also known as the Chetco Effect.
* [[Chinook wind]]s east of the [[Rocky Mountains]] and the [[Cascade Range]] in the United States and Canada, and north, east and west of the [[Chugach Mountains]] of Alaska, United States
* [[Chinook wind]]s east of the [[Rocky Mountains]] and the [[Cascade Range]] in the United States and Canada, and north, east and west of the [[Chugach Mountains]] of Alaska, United States
* Foehn winds in the foothills of the southern Appalachian mountains,<ref>{{cite journal|author=David M. Gaffin|title=Foehn Winds That Produced Large Temperature Differences near the Southern Appalachian Mountains|journal=Weather and Forecasting|date=2007|volume=22|issue=1|pages=145–159|url=https://journals.ametsoc.org/waf/article/22/1/145/38793/Foehn-Winds-That-Produced-Large-Temperature|bibcode=2007WtFor..22..145G|doi=10.1175/WAF970.1|citeseerx=10.1.1.549.7012}}</ref> which can be unusual compared to other Foehn winds in that the relative humidity typically changes little due to the increased moisture in the source air mass<ref>{{cite journal|author=David M. Gaffin|title=Unexpected Warming Induced by Foehn Winds in the Lee of the Smoky Mountains|journal=Weather and Forecasting|date=2002|volume=17|issue=4|pages=907–915|bibcode=2002WtFor..17..907G|doi=10.1175/1520-0434(2002)017<0907:UWIBFW>2.0.CO;2|doi-access=free}}</ref>
* Foehn winds in the foothills of the southern [[Appalachian Mountains]],<ref>{{cite journal|author=David M. Gaffin|title=Foehn Winds That Produced Large Temperature Differences near the Southern Appalachian Mountains|journal=Weather and Forecasting|date=2007|volume=22|issue=1|pages=145–159|url=https://journals.ametsoc.org/waf/article/22/1/145/38793/Foehn-Winds-That-Produced-Large-Temperature|bibcode=2007WtFor..22..145G|doi=10.1175/WAF970.1|citeseerx=10.1.1.549.7012|s2cid=120049170 }}</ref> which can be unusual compared to other Foehn winds in that the relative humidity typically changes little due to the increased moisture in the source air mass<ref>{{cite journal|author=David M. Gaffin|title=Unexpected Warming Induced by Foehn Winds in the Lee of the Smoky Mountains|journal=Weather and Forecasting|date=2002|volume=17|issue=4|pages=907–915|bibcode=2002WtFor..17..907G|doi=10.1175/1520-0434(2002)017<0907:UWIBFW>2.0.CO;2|doi-access=free}}</ref>
*The [[Santa Ana winds]] of southern [[California]], including the [[Sundowner (wind)|Sundowner]] winds of Santa Barbara, are in some ways similar to the Föhn, but originate in dry deserts as a [[katabatic wind]].
*The [[Santa Ana winds]] of southern [[California]], including the [[Sundowner (wind)|Sundowner]] winds of Santa Barbara, are in some ways similar to the Föhn, but originate in dry deserts as a [[katabatic wind]]. However, traditional Föhn conditions frequently prevail along the [[Santa Monica Mountains|Santa Monica]] and [[Santa Ana Mountains|Santa Ana]] Mountains and their respective leeward valleys, the [[San Fernando Valley]] and the [[Riverside County, California|Riverside County]] portion of the [[Inland Empire (California)|Inland Empire]] region.
*[[Puelche (wind)|Puelche wind]] in Chile
*[[Puelche (wind)|Puelche wind]] in Chile
*[[Suêtes]] on the west coast of [[Cape Breton Island]], [[Nova Scotia]], [[Canada]]
*[[Suêtes]] on the west coast of [[Cape Breton Island]], [[Nova Scotia]], [[Canada]]
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;in Asia
;in Asia
* Garmesh, Garmij, Garmbaad (Warm Wind): ({{lang-fa|گرمباد}}, {{lang-glk|گرمش}}) in [[Gilan]] region (near the [[Alborz]]) in the south west of [[Caspian Sea]] in [[Iran]].
* Garmesh, Garmij, Garmbaad ({{Translation|Warm wind|literal=yes}}): ({{langx|fa|گرمباد}}, {{langx|glk|گرمش}}) in [[Gilan]] region (near the [[Alborz]]) in the south west of [[Caspian Sea]] in [[Iran]].
* In winter, a Foehn effect occurs in the [[West Azerbaijan province]], Iran (around [[Lake Urmia]]) as manifested by the province's dry winters relative to those in the windward part of the region (Northern Iraq or [[Kurdistan Region]] and [[Hakkâri Province]] in Turkey). For example, the winter rainfall of [[Urmia]] and [[Salmas]] in [[Iranian Azerbaijan]] is much lower than [[Batifa]] and [[Soran, Iraq|Soran]] in Iraqi Kurdistan, and [[Hakkâri (city)|Hakkâri]] in the Hakkâri Province, which are roughly on the same latitude but are on the windward side of the [[Zagros mountains]].
* In winter, a Foehn effect occurs in the [[West Azerbaijan province]], Iran (around [[Lake Urmia]]) as manifested by the province's dry winters relative to those in the windward part of the region (Northern Iraq or [[Kurdistan Region]] and [[Hakkâri Province]] in Turkey). For example, the winter rainfall of [[Urmia]] and [[Salmas]] in [[Iranian Azerbaijan]] is much lower than [[Batifa]] and [[Soran, Iraq|Soran]] in Iraqi Kurdistan, and [[Hakkâri (city)|Hakkâri]] in the Hakkâri Province, which are roughly on the same latitude but are on the windward side of the [[Zagros Mountains]].
* [[Loo (wind)|Loo]] in [[Indo-Gangetic Plain]]
* [[Loo (wind)|Loo]] in [[Indo-Gangetic Plain]]
*[[Warm Braw]] in the [[Schouten Islands]] north of [[West Papua (province)|West Papua]], Indonesia.<ref>{{cite web|url=http://ggweather.com/winds.html|title=Wind Names|work=ggweather.com}}</ref>
*[[Warm Braw]] in the [[Schouten Islands]] north of [[West Papua (province)|West Papua]], Indonesia.<ref>{{cite web|url=http://ggweather.com/winds.html|title=Wind Names|work=ggweather.com}}</ref>
*[[Wuhan]] in China is famously known as one of the [[Three Furnaces]] on account of its extremely hot weather in summer resulting from the adiabatic warming effect created by mountains further south.
*[[Wuhan]] in China is famously known as one of the [[Three Furnaces]] on account of its extremely hot weather in summer resulting from the adiabatic warming effect created by mountains further south.
*Laos wind ({{lang-vi|gió Lào}}), hot-dry west wind ({{lang-vi|gió tây khô nóng}}) in northern and central [[Vietnam]].
*Laos wind ({{langx|vi|gió Lào}}), hot-dry west wind ({{langx|vi|gió tây khô nóng}}) in northern and central [[Vietnam]].


;in Europe
;in Europe
[[File:Mittagskogel Foehnwolken 15032008 01.jpg|thumb|240px|Foehn clouds upon the [[Karawanken]] mountain range, [[Carinthia]], Austria]]
[[File:Mittagskogel Foehnwolken 15032008 01.jpg|thumb|Foehn clouds upon the [[Karawanken]] mountain range, [[Carinthia]], Austria]]
[[File:Cascada de nubes La Palma 20080606.jpg|thumb|240px|Foehn clouds over [[La Palma]], Spain]]
[[File:Cascada de nubes La Palma 20080606.jpg|thumb|Foehn clouds over [[La Palma]], Spain]]
* Favonio in [[Ticino]] and north-western [[Italy]] due to western and northern winds crossing the [[Alps]] (mostly in winter)
* Favonio in [[Ticino]] and north-western [[Italy]] due to western and northern winds crossing the [[Alps]] (mostly in winter)
*Garbino in the [[Adriatic Sea|Adriatic]] coast of [[Italy]] due to south-western winds crossing the [[Apennine Mountains]] (mostly in fall and winter)
*Garbino in the [[Adriatic Sea|Adriatic]] coast of [[Italy]] due to south-western winds crossing the [[Apennine Mountains]] (mostly in fall and winter)
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* Föhn or Foehn in Austria, southern Germany, [[Switzerland]], [[France]] and [[Liechtenstein]]
* Föhn or Foehn in Austria, southern Germany, [[Switzerland]], [[France]] and [[Liechtenstein]]
*Föhn in [[Ostrobothnia (region)|Ostrobothnia]] and Western [[Lapland (Finland)|Lapland]] in Finland as moist air crosses [[Scandinavian Mountains]] and dries up.
*Föhn in [[Ostrobothnia (region)|Ostrobothnia]] and Western [[Lapland (Finland)|Lapland]] in Finland as moist air crosses [[Scandinavian Mountains]] and dries up.
* [[Halny]] in the [[Carpathian Mountains]], Poland (Central Europe)
* [[Halny]] in the [[Carpathian Mountains]], southern [[Poland]] and northern [[Slovakia]]
*The [[Helm Wind]], on the [[Pennines]] in the [[River Eden, Cumbria|Eden Valley]], [[Cumbria]], England
*The [[Helm Wind]], on the [[Pennines]] in the [[River Eden, Cumbria|Eden Valley]], [[Cumbria]], England
*Hnjúkaþeyr in Icelandic
*Hnjúkaþeyr in Icelandic
*[[Lodos]] wind, causing warm temperatures in the leeward side of mountains in the mild-winter climates of the [[Aegean Sea]], [[Greece]] and [[Turkey]], as well as unusually mild temperatures in locales north of the [[Marmara Sea]] such as [[Istanbul]], [[İzmit|Izmit]] and [[Adapazarı]].
*[[Lodos]] wind, causing warm temperatures in the leeward side of mountains in the mild-winter climate of the [[Aegean Sea]], [[Greece]] and western [[Turkey]], as well as unusually mild temperatures in the cool or moderately cold winter climates north of the [[Marmara Sea]], such as [[Istanbul]], [[Adapazarı]] and [[Zonguldak]].
*[[Košava (wind)|Košava]] (Koshava) wind in Serbia that blows along the Danube River<ref>{{cite journal|last1=Romanić|title=Contributing factors to Koshava wind characteristics|journal=International Journal of Climatology|volume=36|issue=2|pages=956–973|date=2015|doi=10.1002/joc.4397|display-authors=etal|bibcode = 2016IJCli..36..956R |s2cid=129669216 }}</ref><ref>{{cite journal|last1=Romanić|title=Long-term trends of the 'Koshava' wind during the period 1949–2010|journal=International Journal of Climatology|date=2015|volume=35|issue=3|pages=288–302|doi=10.1002/joc.3981|display-authors=etal|bibcode = 2015IJCli..35..288R |s2cid=129402302 }}</ref>
*[[Livas (wind)|Livas]] wind in the [[Thessalian plain]], [[Boeotia]] plain, Plain of Thessaloniki, [[Elefsina]] and [[Athens]] in Greece
*[[Košava (wind)|Košava]] (Koshava) wind in Serbia that blows along the Danube River<ref>{{cite journal|last1=Romanić|title=Contributing factors to Koshava wind characteristics|journal=International Journal of Climatology|volume=36|issue=2|pages=956–973|date=2015|doi=10.1002/joc.4397|display-authors=etal|bibcode = 2016IJCli..36..956R }}</ref><ref>{{cite journal|last1=Romanić|title=Long-term trends of the 'Koshava' wind during the period 1949–2010|journal=International Journal of Climatology|date=2015|volume=35|issue=3|pages=288–302|doi=10.1002/joc.3981|display-authors=etal|bibcode = 2015IJCli..35..288R }}</ref>
*Nortada in [[Cascais]], and most notoriously in [[Guincho Beach]], making it one of the best windsurfing spots in Europe
*Nortada in [[Cascais]], and most notoriously in [[Guincho Beach]], making it one of the best windsurfing spots in Europe
*Ponentà in [[Valencia]] (eastern Spain)
*Ponentà in [[Valencia]] (eastern Spain)
*Terral in [[Málaga]] (southern Spain)
*Terral in [[Málaga]] (southern Spain)
*[[Vântul Mare]] in the [[Carpathian Mountains]], [[Romania]]
*Viento del Sur (Southern Wind) or Hego haizea in Basque in the [[Green Spain|Cantabrian region]] (northern Spain)
*Viento del Sur (Southern Wind) or Hego haizea in Basque in the [[Green Spain|Cantabrian region]] (northern Spain)


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*The [[Australian foehn winds|Great Dividing foehn]] in southeast [[Australia]], leeward of the [[Great Dividing Range]], observed in the [[coastal plains]] of [[New South Wales]], and also in eastern [[Victoria (state)|Victoria]] and eastern [[Tasmania]].<ref>Sharples, J.J. Mills, G.A., McRae, R.H.D., Weber, R.O. (2010) ''Elevated fire danger conditions associated with foehn-like winds in southeastern Australia. Journal of Applied Meteorology and Climatology''.</ref>
*The [[Australian foehn winds|Great Dividing foehn]] in southeast [[Australia]], leeward of the [[Great Dividing Range]], observed in the [[coastal plains]] of [[New South Wales]], and also in eastern [[Victoria (state)|Victoria]] and eastern [[Tasmania]].<ref>Sharples, J.J. Mills, G.A., McRae, R.H.D., Weber, R.O. (2010) ''Elevated fire danger conditions associated with foehn-like winds in southeastern Australia. Journal of Applied Meteorology and Climatology''.</ref>
*The [[Nor'west arch|Nor'wester]] in [[Hawkes Bay]], [[Canterbury, New Zealand|Canterbury]], and [[Otago]], New Zealand<ref>Relph, D. "[https://www.nzgeo.com/stories/the-canterbury-norwester/ The Canterbury nor'wester]," ''New Zealand Geographic''. Retrieved 17 February 2018.</ref>
*The [[Nor'west arch|Nor'wester]] in [[Hawkes Bay]], [[Canterbury, New Zealand|Canterbury]], and [[Otago]], New Zealand<ref>Relph, D. "[https://www.nzgeo.com/stories/the-canterbury-norwester/ The Canterbury nor'wester]," ''New Zealand Geographic''. Retrieved 17 February 2018.</ref>

== In popular culture ==
* The Foehn was mentioned by Queen's lead guitarist Brian May while talking about the band's grim Munich recording studio experience in 1982.<ref>{{cite web|url=http://brianmay.com/brian/briannews/briannewssep12a.html|title=Brian News |date=September 2012|work=brianmay.com}}</ref>
* The foehn is attributed by the narrator of [[Jens Bjørneboe]]'s 1966 novel ''Frihetens øyeblikk'' (''Moment of Freedom'') as the traditional cause of occasional unprovoked murders in a small Alpine town.<ref>{{Cite book|last=Bjørneboe|first=Jens|title=Frihetens øyeblikk|publisher=Gyldendal Norsk Forlag|year=1966|isbn=8205234841|location=Oslo|pages=32–33, 180–185}}</ref>
* "Foehn" is the last word in ''A Nest of Ninnies'', a 1969 novel by [[John Ashbery]] and [[James Schuyler]]. Ashbery claimed that he and Schuyler chose this particular word because "people, if they bothered to, would have to open the dictionary to find out what the last word in the novel meant."<ref>{{cite magazine|url=http://www.theparisreview.org/interviews/3014/the-art-of-poetry-no-33-john-ashbery|title=The Art of Poetry No. 33 |author=John Ashbery|volume=Winter 1983|issue=90|magazine=theparisreview.org|year=1983}}</ref>
*[[Fønfjord]], meaning "Foehn Fjord," was named by Arctic explorer [[Carl Ryder]] after the powerful Foehn wind gusts blowing during the first exploration of the fjord in August 1891.<ref name="cat">{{Cite web|url=https://data.geus.dk/geusmap/?mapname=stednavnedb#baslay=baseMapGl&optlay=&extent=549832.8357720698,8582739.868248867,622444.3190166993,8680765.370629115&layers=grl_geus_north_east_higgins_map,grl_ne_higgins_placenames,grl_ne_placenames&filter_1=txt_search.part=&placename=&filter_2=txt_search.part=&placename=|title=Place names, northern East Greenland|website=data.geus.dk}}</ref>


==Gallery==
==Gallery==
<gallery>
<gallery widths="180px" class="center">
File:Pájara Morro Jable - Carretera Punta de Jandía - cemetery + foehn 01 ies.jpg|Foehn over Carretera Punta de Jandía in [[Morro Jable]], [[Pájara]], [[Fuerteventura]], Canary Islands
File:Pájara Morro Jable - Carretera Punta de Jandía - cemetery + foehn 01 ies.jpg|Foehn over Carretera Punta de Jandía in [[Morro Jable]], [[Pájara]], [[Fuerteventura]], Canary Islands
File:La Palma - El Paso - Cumbre Nueva+Foehn (Mirador Llano del Jable) 01 ies.jpg|Dissolving clouds from Foehn wind over the Cumbre Nueva in [[El Paso, La Palma]], Canary Island
File:La Palma - El Paso - Cumbre Nueva+Foehn (Mirador Llano del Jable) 01 ies.jpg|Dissolving clouds from Foehn wind over the Cumbre Nueva in [[El Paso, La Palma]], Canary Island
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* [[Alpine climate]]
* [[Alpine climate]]
* [[Anabatic wind]]
* [[Anabatic wind]]
* [[Chinook wind]]
* [[Föhn cloud]]
* [[Föhn cloud]]
* [[Katabatic wind]]s
* [[Katabatic wind]]s
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* [https://www.flickr.com/photos/snowfactory/2756402718/ Movie of a Föhn situation in the Swiss Alps]
* [https://www.flickr.com/photos/snowfactory/2756402718/ Movie of a Föhn situation in the Swiss Alps]
* [http://www.bbc.co.uk/weather/feeds/17448378 East Scotland warmth due to Foehn Effect]
* [http://www.bbc.co.uk/weather/feeds/17448378 East Scotland warmth due to Foehn Effect]
* [http://www.meteocentrale.ch/de/wetter/foehn-und-bise/foehn.html Foehn chart provided by meteomedia/meteocentrale.ch]
* [http://www.meteocentrale.ch/de/wetter/foehn-und-bise/foehn.html Foehn chart provided by meteomedia/meteocentrale.ch] {{Webarchive|url=https://web.archive.org/web/20130403060503/http://www.meteocentrale.ch/de/wetter/foehn-und-bise/foehn.html |date=2013-04-03 }}


{{Authority control}}
{{Authority control}}

Revision as of 05:48, 11 November 2024

The causes of the Foehn effect in the lee of mountains (adapted from: [1])
Dissolving Föhn clouds over Cumbre Nueva, La Palma, at an elevation of 1,400 m (4,600 ft)

A Foehn, or Föhn (UK: /fɜːn/, US: /fn/ fayn,[2][3] US also /fʌn, fɜːrn/ fu(r)n[4][5]), is a type of dry, relatively warm downslope wind in the lee of a mountain range. It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped most of its moisture on windward slopes (see orographic lift). As a consequence of the different adiabatic lapse rates of moist and dry air, the air on the leeward slopes becomes warmer than equivalent elevations on the windward slopes.

Foehn winds can raise temperatures by as much as 14 °C (25 °F)[6] in just a matter of hours. Switzerland, southern Germany, and Austria have a warmer climate due to the Foehn, as moist winds off the Mediterranean Sea blow over the Alps.

Etymology

The name Foehn (German: Föhn, pronounced [ˈføːn]) arose in the Alpine region. Originating from Latin (ventus) favonius, a mild west wind of which Favonius was the Roman personification[7] and probably transmitted by Romansh: favuogn or just fuogn, the term was adopted as Old High German: phōnno. In the Southern Alps, the phenomenon is known as Föhn but also Italian: favonio and fen in Serbo-Croatian and Slovene. The German word Föhn (pronounced the same way) also means 'hairdryer', while the word Fön is a genericized trademark today owned by AEG.[8] The form phon is used in French-speaking parts of Switzerland as well as in Italy.

The name Föhn was originally used to refer to the south wind which blows during the winter months and brings thaw conditions to the northern side of the Alps. Because Föhn later became a generic term that was extended to other mountain ranges around the world that experience similar phenomena, the name "Alpine föhn" (Alpenföhn) was coined for the Föhns of the Alpine region.[9]

Causes

The warm moist air from northern Italy is blocked on the windward side, loses much of its water vapour content, and descends on the French plateau and valley of the Mont-Cenis range in the Maurienne valley.

There are four known causes of the Foehn warming and drying effect.[1] These mechanisms often act together, with their contributions varying depending on the size and shape of the mountain barrier and on the meteorological conditions, such as the upstream wind speed, temperature and humidity.

Condensation and precipitation

When winds blow over elevated terrain, air forced upwards expands and cools due to the decrease in pressure with height. Since colder air can hold less water vapour, moisture condenses to form clouds and precipitates as rain or snow on the mountain's upwind slopes. The change of state from vapour to liquid water releases latent heat energy which heats the air, partially countering the cooling that occurs as the air rises. The subsequent removal of moisture as precipitation renders this heat gain by the air irreversible, leading to the warm, dry, Foehn conditions as the air descends in the mountain's lee. This mechanism has become a popular textbook example of atmospheric thermodynamics. However, the common occurrence of 'dry' Foehn events, where there is no precipitation, implies there must be other mechanisms.

Rotor cloud revealing overturning and turbulence above the lee slopes of the Antarctic Peninsula during a westerly Foehn event

Isentropic draw-down

Isentropic draw-down is the draw-down of warmer, drier air from aloft. When the approaching winds are insufficiently strong to propel the low-level air up and over the mountain barrier, the airflow is said to be 'blocked' by the mountain and only air higher up near mountain-top level is able to pass over and down the lee slopes as Foehn winds. These higher source regions provide Foehn air that becomes warmer and drier on the leeside after it is compressed with descent due to the increase in pressure towards the surface.

Mechanical mixing

When river water passes over rocks, turbulence is generated in the form of rapids, and white water reveals the turbulent mixing of the water with the air above. Similarly, as air passes over mountains, turbulence occurs and the atmosphere is mixed in the vertical. This mixing generally leads to a downward warming and upward moistening of the cross-mountain airflow, and consequently to warmer, drier Foehn winds in the valleys downwind.

Radiative warming

Dry Foehn conditions are responsible for the occurrence of rain shadows in the lee of mountains, where clear, sunny conditions prevail. This often leads to greater daytime radiative (solar) warming under Foehn conditions. This type of warming is particularly important in cold regions where snow or ice melt is a concern or where avalanches are a risk.

Effects

Winds of this type are also called "snow-eaters" for their ability to make snow and ice melt or sublimate rapidly. This is a result not only of the warmth of Foehn air, but also its low relative humidity. Accordingly, Foehn winds are known to contribute to the disintegration of ice shelves in the polar regions.[10]

Foehn winds are notorious among mountaineers in the Alps, especially those climbing the Eiger, for whom the winds add further difficulty in ascending an already difficult peak.

They are also associated with the rapid spread of wildfires, making some regions which experience these winds particularly fire-prone.

Purported physiological effects

Anecdotally, residents in areas of frequent Foehn winds have reported experiencing a variety of illnesses ranging from migraines to psychosis. The first clinical review of these effects was published by the Austrian physician Anton Czermak in the 19th century.[11] A study by the Ludwig-Maximilians-Universität München found that suicide and accidents increased by 10 percent during Foehn winds in Central Europe.[citation needed] The causation of Föhnkrankheit (English: Foehn-sickness) is unproven. Labels for preparations of aspirin combined with caffeine, codeine and the like will sometimes include Föhnkrankheit amongst the indications.[citation needed][12] Evidence for effects from Chinook winds remains anecdotal, as it does for New Zealand's Nor'wester.[13]

In some regions, Foehn winds are associated with causing circulatory problems, headaches, or similar ailments.[14] Researchers have found, however, the Foehn wind's warm temperature to be beneficial to humans in most situations, and have theorised that the reported negative effects may be a result of secondary factors, such as changes in the electrical field or in the ion state of the atmosphere, the wind's relatively low humidity, or the generally unpleasant sensation of being in an environment with strong and gusty winds.[14]

Local examples

Regionally, these winds are known by many different names. These include:

in Africa
in the Americas
in Antarctica
in Asia
in Europe
Foehn clouds upon the Karawanken mountain range, Carinthia, Austria
Foehn clouds over La Palma, Spain
in Oceania

See also

References

  • McKnight, TL & Hess, Darrel (2000). "Foehn/Chinook Winds". In Physical Geography: A Landscape Appreciation, p. 132. Upper Saddle River, NJ: Prentice Hall. ISBN 0-13-020263-0.

Footnotes

  1. ^ a b Elvidge, Andrew D.; Renfrew, Ian A. (14 May 2015). "The Causes of Foehn Warming in the Lee of Mountains". Bulletin of the American Meteorological Society. 97 (3): 455–466. Bibcode:2016BAMS...97..455E. doi:10.1175/bams-d-14-00194.1.
  2. ^ Jones, Daniel (2011). Roach, Peter; Setter, Jane; Esling, John (eds.). Cambridge English Pronouncing Dictionary (18th ed.). Cambridge University Press. ISBN 978-0-521-15255-6.
  3. ^ Wells, John C. (2008). Longman Pronunciation Dictionary (3rd ed.). Longman. ISBN 978-1-4058-8118-0.
  4. ^ Upton, Clive; Kretzschmar, William A. Jr. (2017). The Routledge Dictionary of Pronunciation for Current English (2nd ed.). Routledge. ISBN 978-1-138-12566-7.
  5. ^ "foehn". Merriam-Webster.com Dictionary. Merriam-Webster. Retrieved 2022-03-17.
  6. ^ "South Dakota Weather History and Trivia for January". National Weather Service Weather Forecast Office. February 8, 2006. See January 22 entry.
  7. ^ Concise Oxford Dictionary, 10th edition, Oxford University Press, entry föhn.
  8. ^ "22. Januar 2009 – Vor 100 Jahren: "Fön" ins Markenregister eingetragen". WDR.de. 2009-01-22. Retrieved 2019-12-21.
  9. ^ Der Brockhaus. Wetter und Klima. Seite 101, Brockhaus, Leipzig/Mannheim, 2009, ISBN 978-3-7653-3381-1
  10. ^ Elvidge, Andrew D.; Renfrew, Ian A.; King, John C.; Orr, Andrew; Lachlan-Cope, Tom A. (January 2016). "Foehn warming distributions in nonlinear and linear flow regimes: a focus on the Antarctic Peninsula" (PDF). Quarterly Journal of the Royal Meteorological Society. 142 (695): 618–631. Bibcode:2016QJRMS.142..618E. doi:10.1002/qj.2489.
  11. ^ Giannini, AJ; Malone, DA; Piotrowski, TA (1986). "The serotonin irritation syndrome – a new clinical entity?". The Journal of Clinical Psychiatry. 47 (1): 22–25. PMID 2416736.
  12. ^ See the documentary: Snow Eater (the English translation of Canadian First Nations word phonetically pronounced chinook). telefilm.ca Archived 2013-10-17 at the Wayback Machine.
  13. ^ Brook, K., "Grumpy nor'west winds," University of Canterbury, 2 December 2014. Retrieved 22 November 2023.
  14. ^ a b Tuller, Stanton E. (April 1980). "The Effects of a Foehn Wind on Human Thermal Exchange: The Canterbury Nor'wester". New Zealand Geographer. 36 (1): 11–19. Bibcode:1980NZGeo..36...11T. doi:10.1111/j.1745-7939.1980.tb01919.x.
  15. ^ David M. Gaffin (2007). "Foehn Winds That Produced Large Temperature Differences near the Southern Appalachian Mountains". Weather and Forecasting. 22 (1): 145–159. Bibcode:2007WtFor..22..145G. CiteSeerX 10.1.1.549.7012. doi:10.1175/WAF970.1. S2CID 120049170.
  16. ^ David M. Gaffin (2002). "Unexpected Warming Induced by Foehn Winds in the Lee of the Smoky Mountains". Weather and Forecasting. 17 (4): 907–915. Bibcode:2002WtFor..17..907G. doi:10.1175/1520-0434(2002)017<0907:UWIBFW>2.0.CO;2.
  17. ^ "Wind Names". ggweather.com.
  18. ^ Romanić; et al. (2015). "Contributing factors to Koshava wind characteristics". International Journal of Climatology. 36 (2): 956–973. Bibcode:2016IJCli..36..956R. doi:10.1002/joc.4397. S2CID 129669216.
  19. ^ Romanić; et al. (2015). "Long-term trends of the 'Koshava' wind during the period 1949–2010". International Journal of Climatology. 35 (3): 288–302. Bibcode:2015IJCli..35..288R. doi:10.1002/joc.3981. S2CID 129402302.
  20. ^ Sharples, J.J. Mills, G.A., McRae, R.H.D., Weber, R.O. (2010) Elevated fire danger conditions associated with foehn-like winds in southeastern Australia. Journal of Applied Meteorology and Climatology.
  21. ^ Relph, D. "The Canterbury nor'wester," New Zealand Geographic. Retrieved 17 February 2018.