There will be no foehn effect in mountainous areas. What are the conditions of foehn effect?

Foehn 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.

When the airflow is perpendicular to the hillside or the included angle is large, the wet airflow will pass through the hillside, which will have different effects on the temperature and precipitation of windward slope and leeward slope.

For example, if there is an airflow going through a mountain with a height of 4000m, suppose the temperature at the foot of the windward slope is 15℃ and the condensation height is 1000m. Since the temperature drops 1℃ every time the air rises 1000 m below the condensation height, it is at the height of1000 m. Above the condensation height, if the temperature rises by 100 m and drops by 0 or 6℃, it will drop to-13℃. If the condensed water vapor completely falls to the front of the mountain, the air will become a dry air mass after crossing the mountains and mountains. Without the influence of water vapor, every time the temperature drops by 100 m, the air flow will increase by 1℃. When the airflow reaches the foot of the mountain, it will become a dry and hot wind at 27℃.