A föhn wind or foehn wind occurs when a deep layer of prevailing wind is forced over a mountain range (Orographic lifting). As the wind moves upslope, it expands and cools, causing water vapor to precipitate out. This dehydrated air then passes over the crest and begins to move downslope. As the wind descends to lower levels on the leeward side of the mountains, the air heats as it comes under greater atmospheric pressure creating strong, gusty, warm and dry winds. Föhn winds can raise temperatures as much as 30°C (54°F) in just a matter of hours. Winds of this type are called "snow-eaters" for their ability to make snow melt rapidly. This ability is based not only on high temperature, but also the low relative humidity of the air mass. Föhn winds are also associated with the rapid spread of wildfires, making some regions which experience these winds particularly fire-prone.

The name föhn (from the German Föhn, pronounced ) originated in the Alps, and central Europe enjoys a warmer climate due to them. Föhn winds are notorious among mountaineers in the Alps, especially those climbing the Eiger, for whom the winds add additional difficulty in ascending an already difficult peak. AEG registered the trademark Fön in the 1920s for its hairdryer, which is widely used as a synonym in the German language.

These winds are often associated in popular mythology with illness ranging from migraines to psychosis. The Santa Ana winds are often called "the murder winds." A study by the Ludwig-Maximilians-Universität München found that suicide and accidents increased by 10 percent during föhn winds in Central Europe. The causation of Föhnkrankheit (English: Föhn-sickness), however, remains to be proven.

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

• Zonda winds in Argentina
• Chinook winds in the Rocky Mountains, United States/Canada and the Chugach Mountains of Alaska, United States
• Diablo winds in the San Francisco Bay Area, United States
• Santa Ana winds in Southern California, United States
• The Nor'wester in southern New Zealand
• Halny in the Carpathians
• Fogony in the Catalan Pyrenees
• Bergwind in South Africa.

See also

• Katabatic winds

References

• McKnight, TL & Hess, Darrel (2000). Foehn/Chinoonk Winds. In , Physical Geography: A Landscape Appreciation, pp. 132. Upper Saddle River, NJ: Prentice Hall. ISBN 0130202630

External links

• Illustration

Winds | German loanwords

Efecte Föhn | Föhn | Föön | Efecto Foehn | Vento de Föhn | Fœhn | Foehn | Föhn (wind) | フェーン現象 | Fønvind | Fønvind | Fen | Фён | Föhntuuli | Föhn | Фен | 焚風