What is the cause of foehn effect?

The so-called "foehn effect" refers to a kind of dry-hot wind formed by the continuous decrease of height and rising temperature when the air sinks again.

Foehn effect is mainly measured from the angle of temperature and dry humidity. Foehn is also a dry and hot wind. There are two conditions to form foehn. The first condition is that the air temperature is high, which needs to be achieved through the sinking movement of the air. Under normal circumstances, the air temperature will rise by about 6.5℃ every time the altitude drops 1000m, so when the sinking motion of the air seat exceeds about 1000m, there will be a certain foehn effect, and with the increase of altitude drop, the foehn effect will become more obvious. If the drop exceeds 3000 meters,

Foehn winds often appear in the form of gusts, blowing down from the mountain along the hillside. Foehn first refers to the dry and hot wind formed in the valleys of Germany, Austria and Switzerland after the airflow crossed the Alps. The Rocky Mountains in America and the Caucasus Mountains in Russia are as famous as the Alps. It can also be seen in all parts of China, such as the leeward slopes of Himalayas, Hengduan Mountain and Erlang Mountain, which have a strong foehn effect. Shijiazhuang is located at the eastern foot of Taihang Mountain, and the average annual wind burning time is 19 days, with the maximum year reaching 49 days.