Alps and Climate


Alps and Climate

In a mountainous mid-latitude region, natural resources like water or energy, but also tourism strongly depend on climate and weather. Temperature, solar radiation, drought or strong precipitation events are determining factors.

by Martine Rebetez and Isabelle Morier, WSL - Swiss Federal Institute for Forest, Snow and Landscape Research

Due to their altitude, the Alps are typical locations for glaciers, snow or permafrost, all phenomena that can also be observed at higher latitudes. Mountainous regions mean steep slopes and the origin of rivers, but they also mean avalanches, mud or debris flows (mass of water and earth materials flowing down a stream). They are thus very sensitive to any change in temperature or precipitation, or more generally, to global climate change. In the future, it can be expected that melting glaciers and permafrost, a higher snow limit and stronger precipitation events will have important human, ecological and economic consequences in the Alps.
Further Readings & Links

A future scenario from a hydrologic point of view.

The paper elaborates the Kyoto Protocol in a profound and comprehensible way.

Situation and Challenges

The Alpine chain extends from the Mediterranean coast in the South to Austria in the North. In spite of this latitudinal gradient, its mountainous character strongly defines its climate. Temperature decreases together with altitudinal increase. The topographic gradient can be compared with a latitudinal gradient: 100m increase in elevation is about equivalent to an increase of 1° of latitudse towards the North.

Mountainous regions typically experience strong daily and seasonal contrasts. At a smaller scale, the temperature gradient as well as the daily or seasonal contrasts are influenced by orientation and solar radiation. At local or regional scale, precipitation increases with altitude, as pressure and temperature decrease in air masses forced to the summits. In the ascending air mass, condensation of water vapour ends up into rain or snow, depending on the temperature. On the other side of the relief, subsiding air dries up rapidly and its temperature increases faster than it had decreased on the ascending side. Surprisingly warm temperatures and winds are experienced in Alpine valleys and usually referred to as "foehn" phenomena. Precipitation takes place all over the year in the whole Alpine chain, even in the Mediterranean Alps where thunderstorms bring rain also during the summer, while the surrounding plains normally experience dry summers typical to the Mediterranean climate.

The graphic describes the dynamics of the foehn wind which occurs when a deep layer of prevailing wind is forced over a mountain range (Orographic lifting) (Source: German Wikipedia, H.-P. HEIN).

Natural phenomena characteristic to the Alpine domain such as glaciers, permafrost or specific Alpine vegetation depend directly on the climate. Climate change may have particularly strong impacts in the Alps. Warmer temperatures, less snow and more frequent heavy precipitation are expected in the future. Particularly in connection with glacier melting and thawing permafrost, this can lead to catastrophes such as land slides, mud- or debris flows.
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