The wind is a phenomenon (named after a characteristic wind from the north of the Alps) occurs and relieves the mountainous when a mass of warm and humid air is lifted to overcome that obstacle. This causes the water vapor to cool down and undergo a process of condensation or reverse sublimation, precipitating on the windward slopes where clouds and orographic rains form. While this occurs there is a strong climatic contrast between the slopes, with high humidity and rains on the windward slopes, and the leeward slopes in which the weather is clear and the temperature is increasing due to the adiabatic compression process.
This process is motivated because the dry and warm air descends rapidly due to the rain, heating up a measure that increases the pressure when descending and with extremely low humidity. The effect is the process described in the leeward blades and results in the wind.
Very often, all the moisture coming from the windward slopes does not turn into clouds and rain, but rather a large part of those clouds pass to the leeward side, where it moves with a totally inverse process that occurred on the windward side. Indeed, orographic clouds that descend on the leeward side heat up and disappear at a certain height when the dew point temperature is exceeded. In this way, a type of cloud is formed that forms a kind of ceiling in which the temperature contrasts can be very strong with very little variation in height.
It is formed as follows:
- The air mass is first cooled by dry adiabatic degree (GAS) at a rate of 1 degree Celsius for every 100 meters of ascent.
- After this phase, once the dew point has been exceeded, it continues to cool down more but now according to the wet adiabatic gradient (GAH), a ratio of 0.6 ° C per 100 meters, producing precipitation.
- Once a temperature of 15 ° C is obtained by simple mathematical calculation, exceeding the rock point at about 2,000 meters (for example), the air mass is cooled according to the GAH, obtaining an air mass close to 0 ° C Upon reaching the summit Once the relief is overcome, the air mass begins a descending descent, heating up according to the GAS, which gives a result of more than 30 ° C when it reaches the area shaded by the rain.
