Foehn wind
A Foehn or Föhn (
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 (
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
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.
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
This section needs additional citations for verification. (February 2013) |
Winds of this type are also called "snow-eaters" for their ability to make snow and ice melt or
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
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
This section needs additional citations for verification. (February 2018) |
Regionally, these winds are known by many different names. These include:
- in Africa
- Bergwindin South Africa
- in the Americas
- The Brookings Effecton the southwestern coast of Oregon, also known as the Chetco Effect.
- Chinook winds 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
- The Inland Empireregion.
- Puelche wind in Chile
- Newfoundland, Newfoundland and Labrador, Canada
- Zonda winds in Argentina
- in Antarctica
- Föhn wall on South Orkneys
- in Asia
- Garmesh, Garmij, Garmbaad (lit. transl. Warm wind): (.
- In winter, a Foehn effect occurs in the Zagros mountains.
- Loo in Indo-Gangetic Plain
- Schouten Islands north of West Papua, Indonesia.[17]
- 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 (Vietnamese: gió Lào), hot-dry west wind (Vietnamese: gió tây khô nóng) in northern and central Vietnam.
- in Europe
- Favonio in Ticino and north-western Italy due to western and northern winds crossing the Alps (mostly in winter)
- Garbino in the Adriatic coast of Italy due to south-western winds crossing the Apennine Mountains (mostly in fall and winter)
- Fen in northwest Slovenia
- Fønvind in South Norway, in particular Central Norway, resulting in extreme winter warming, including Scandinavia's warmest winter temperature in Sunndalsøra.
- Fogony in the Catalan Pyrenees
- Föhn or Foehn in Austria, southern Germany, Switzerland, France and Liechtenstein
- Föhn in Ostrobothnia and Western Lapland in Finland as moist air crosses Scandinavian Mountains and dries up.
- Halny in the Carpathian Mountains, southern Poland and northern Slovakia
- The Helm Wind, on the Pennines in the Eden Valley, Cumbria, England
- Hnjúkaþeyr in Icelandic
- .
- Košava (Koshava) wind in Serbia that blows along the Danube River[18][19]
- Nortada in Guincho Beach, making it one of the best windsurfing spots in Europe
- Ponentà in Valencia (eastern Spain)
- Terral in Málaga (southern Spain)
- Viento del Sur (Southern Wind) or Hego haizea in Basque in the Cantabrian region(northern Spain)
- in Oceania
- The
- The
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.[22]
- 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.[23]
- "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".[24]
- 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.[25]
Gallery
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Dissolving clouds from Foehn wind over the Cumbre Nueva in El Paso, La Palma, Canary Island
-
Foehn over Llano del Jable
-
Foehn can be initiated when deep low-pressure systems move into Europe, drawing moistMediterranean air over the Alps.
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
- ^ .
- ISBN 978-0-521-15255-6.
- ISBN 978-1-4058-8118-0.
- ISBN 978-1-138-12566-7.
- ^ "foehn". Merriam-Webster.com Dictionary. Retrieved 2022-03-17.
- ^ "South Dakota Weather History and Trivia for January". National Weather Service Weather Forecast Office. February 8, 2006. See January 22 entry.
- ^ Concise Oxford Dictionary, 10th edition, Oxford University Press, entry föhn.
- ^ "22. Januar 2009 – Vor 100 Jahren: "Fön" ins Markenregister eingetragen". WDR.de. 2009-01-22. Retrieved 2019-12-21.
- ISBN 978-3-7653-3381-1
- doi:10.1002/qj.2489.
- PMID 2416736.
- ^ 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.
- ^ Brook, K., "Grumpy nor'west winds," University of Canterbury, 2 December 2014. Retrieved 22 November 2023.
- ^ .
- S2CID 120049170.
- .
- ^ "Wind Names". ggweather.com.
- S2CID 129669216.
- S2CID 129402302.
- ^ 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.
- ^ Relph, D. "The Canterbury nor'wester," New Zealand Geographic. Retrieved 17 February 2018.
- ^ "Brian News". brianmay.com. September 2012.
- ISBN 8205234841.
- ^ John Ashbery (1983). "The Art of Poetry No. 33". theparisreview.org. Vol. Winter 1983, no. 90.
- ^ "Place names, northern East Greenland". data.geus.dk.
External links
- Photo of Föhnmauer The strong clouds at the mountain ridges where the Föhn winds form are called Föhnmauer (Föhn wall).
- Illustration
- Movie of a Föhn situation in the Swiss Alps
- East Scotland warmth due to Foehn Effect
- Foehn chart provided by meteomedia/meteocentrale.ch Archived 2013-04-03 at the Wayback Machine