Normally, the air descending down the side of a mountain heats up and the wind speed decreases. This wind is called Föhn. Schematic link https://atlasprirodirossii.ru/veter-fen-i-ego-sekret-dlya-cheloveka/. Sometimes the foehn turns into a cold mistral wind and its speed increases downhill. This happens only in those places where the lee side of the mountain is very steep. Link to two photos where the mistral occurs https://en.wikipedia.org/wiki/Mont_Ventoux. Most often, such a wind occurs on the coast. In the Black Sea, this is the Novorossiysk mistral (Bora). We conducted a study and found that at the foot of a steep leeward slope of a mountain, when a jet of air is separated from the slope, a "vacuum" is formed. It is associated with a decrease in air temperature and increases the pressure gradient down the mountainside. The temperature can drop from positive to minus 15 degrees. The wind can increase up to 60 m/s. Check out our article file:///C:/Users/User/Downloads/texc_2015_4(1)__7.pdf.
On the Black Sea coast in the Novorossiysk region, the Mistral is provoked by the winter upwelling of warm waters in the sea. The appearance of warm water on the surface of the sea increases the atmospheric pressure gradient between the sea and land. The wind is getting stronger. When the wind intensifies from a depth, warm water rises and the pressure gradient increases, and the wind speed becomes catastrophic. Links to photos https://www.yugopolis.ru/news/incidents/2012/02/09/29694/novorossiisk-stihiya-uragan https://ki-news.ru/2021/01/21/bora-moj- drug-bora-foto-s-historiej-ot-fotografa-ki/
Borys Kapochkin The Mistral is a chilly, dry wind that sweeps over the Mediterranean area, notably in France, from the northwest to the southeast. It is a downslope wind, which means it blows from the mountains down to the sea.
Because it does not occur in the same way as a Föhn wind, the Mistral is not a warm mountain wind (Föhn). When moist, chilly air on the windward side of the mountains is lifted and chilled, causing the moisture to condense and create clouds, a Föhn wind sweeps down the leeward side of the mountains. Due to adiabatic heating, the air drops on the leeward side of the mountains and heats.
The Mistral, on the other hand, is created by the lifting and cooling of wet air across a mountain range. The pressure differential between a high-pressure system over the Atlantic Ocean and a low-pressure system over the Mediterranean Sea is what causes it. As the high-pressure system advances eastward, winds blow from the northwest to the southeast, bringing cold, dry air from the continent's core to the shore.
As a result, the Mistral is not a warm mountain wind (Föhn) since it is produced by different physical processes than a Föhn wind.
Dear Qamar Ul Islam. You're wrong. Look at the graphs (green color wind speed, red color air temperature) of changes in air temperature and wind speed from the lee side of the mountain (photo) in Novorossiysk (Black Sea) before the orographic wind of catamtrophic force on February 7, 2012 (https://cyberleninka.ru /article/n/ekstremalnaya-bora-7-8-fevralya-2012-g-v-rayone-g-novorossiysk-i-ee-prognoz-po-modeli-cosmo-ru/viewer). I have attached the synoptic map. There are three arrows on the chart. These are three increases in wind speed on the lee side of the mountain. The first two cases are foehn; the third case is an orographic wind of the Mistral type. Sincerely, Boris.
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