What does the foehn effect mean? What is the reason?

Foehn is a form of local air movement caused by mountains, which appears on the back of mountains-the airflow over mountains sinks on the leeward slope and becomes dry and hot. Foehn winds often appear in the form of gusts, blowing down from the mountain along the hillside.

What is the foehn effect? When humid air crosses a mountain, it often forms a dry and high-temperature airflow on the lee slope of the mountain, which is called foehn. Foehn winds often appear in the form of gusts, blowing down from the mountain along the hillside. The whole process of foehn forming clouds and rain on windward slope and dry hot wind on leeward slope is called "foehn effect".

Generally speaking, when the airflow is blocked by mountains, it will climb or bypass. When the airflow rises on the windward slope, the temperature will decrease. Air rises to a certain height, condenses when it meets cold water vapor, and falls in the form of rain and snow. When the air reaches the ridge, it becomes dry, descends along the leeward slope, and the temperature increases with the dry adiabatic rate. Therefore, when the air sinks to the foothills along the mountain, the temperature often rises sharply. When the foehn wind is strong, it often brings a series of disasters.

Foehn effect is a unique weather phenomenon in mountainous areas. It was caused by the sinking of the airflow after crossing the mountain. When a mass of air sinks from the sky to the ground, the temperature rises by an average of 6.5 degrees Celsius for every drop of 1000 meters. That is to say, when the air falls to the ground from a mountain with an altitude of 4000 meters to 5000 meters, the temperature will rise by more than 20 degrees Celsius, making the cool climate suddenly hot, which is the reason for "burning wind". For example, the foehn in Taitung, Taiwan, was formed when the southwest airflow crossed the central mountain range, and the water vapor was blocked and evaporated, forming a dry and hot foehn.