Foehn wind

Definition of Foehn Wind

Foehn wind, also spelled Föhn wind, represents a warm, arid down-slope wind that develops on the leeward, or downwind, side of a mountain range. This specific type of wind surfaces due to adiabatic heating of air that has divested the majority of its moisture on windward slopes. Because of the divergent adiabatic lapse rates of moist and dry air, the air on the leeward slopes attains a higher temperature than air located at a comparable altitude on the windward side.

Formation of Foehn Winds

Foehn winds commence when moist air is propelled over a mountain range. As the air ascends and cools, it condenses, losing its moisture in the guise of rain or snow on the windward side of the mountains, an event identified as orographic lift.

Following this moisture depletion, the dry air begins its downward journey on the reverse side of the mountain, the leeward side. As this air descends, it experiences compression and heating, a process denoted as adiabatic warming. The result is a warm, dry wind cascading over the valleys and plains situated beyond the mountain range.

Effects of Foehn Winds

Foehn winds can significantly alter local climatic conditions and have profound repercussions on human activities. They can introduce notably warm weather during cooler seasons, but can also induce rapid temperature increases, prompting snowmelt and localized flooding.

These winds carry the capacity to severely impact wildfire behavior, hastening spread due to the hot, dry conditions they engender. In alpine locales, Foehn winds can instigate avalanches resulting from rapid warming.

Foehn sickness pertains to a set of health symptoms that include headaches and migraines, irritability, and fatigue that are linked by some to the Foehn winds, although the evidence to substantiate this link is not unequivocal.

Foehn Winds Around the World

Foehn winds acquire different names in various regions of the world. In North America, particularly within the Rocky Mountains, they are termed Chinook winds. In Argentina, they go by the name Zonda winds, and in New Zealand, they are referred to as the Nor'west arch. Despite the variations in terminology, all these winds retain the foundational characteristics inherent to a conventional Foehn wind.