Föhns

Föhns are warm, dry downslope winds that occur on the leeside of mountain ranges. They are most commonly described in the European Alps, but similar winds occur in other mountain regions, including the Pyrenees, the Rockies, the Andes, and the Himalayas. The term föhn originates from the German Föhnwind and is used in meteorology to describe this category of wind regardless of location.

The core mechanism involves air moving over a mountain barrier. As moist air ascends the windward slope, it cools and its moisture condenses, often producing precipitation on the windward side. When the air reaches the crest and descends on the leeward side, it compresses and warms adiabatically while the relative humidity drops, producing a warm and dry wind that can raise surface temperatures rapidly. Depending on atmospheric conditions, the warming can be strong, and the wind can be gusty. The passage of a föhn is often followed by clearing skies.

Föhn winds are associated with characteristic weather changes, including rapid temperature increases and drops in humidity. They can influence snow stability and avalanche risk in winter and may affect weather-sensitive activities such as aviation and agriculture. The phenomenon has regional variants and related winds in other mountain regions, such as the Chinook in North America and the Zonda in Argentina, all sharing the same basic drying and warming downslope process.

In scientific literature, föhns are studied as part of mountain meteorology and synoptic-scale wind interactions, illustrating how orography modulates local climate and weather patterns.