Foehn

A föhn or foehn is a type of dry, warm, down-slope wind that occurs in the 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 rates of moist and dry air, the air on the leeward slopes becomes warmer than equivalent elevations on the windward slopes. Föhn winds can raise temperatures by as much as 14 °C (25 °F) in just a matter of minutes. Central Europe enjoys a warmer climate due to the Föhn, as moist winds off the Mediterranean Sea blow over the Alps.

In German-speaking countries, where popular superstition attributes all kinds of illnesses to various movements of air, the föhn is associated with causing "circulatory problems" and headaches. There is no scientific proof of such a link.

Winds of this type are also called "snow-eaters" for their ability to make snow melt or sublimate rapidly. This snow-removing ability is caused not only by warmer temperatures, but also the low relative humidity of the air mass having been stripped of moisture by orographic precipitation coming over the mountain(s).

Föhn 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.

Anecdotally, residents in areas of frequent föhn winds report 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. 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) is yet unproven. Labeling for preparations of aspirin combined with caffeine, codeine and the like will sometimes include Föhnkrankheit amongst the indications. Evidence for effects from Chinook winds remain anecdotal.

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Wikipedia