Why does it snow in the Sahara desert?

The Sahara desert has always been the hottest area in the world, where the highest temperature is as high as 58 degrees. Recently, some netizens said that it snowed in the Sahara desert! This news surprised the netizens who had never killed. As we all know, the Sahara desert is hot and dry, and it doesn't even rain several times all the year round. Why is it snowing? But recently, a photographer really uploaded a photo of snow in the Sahara desert on the Internet.

It is reported that on February 22nd, 12, the snow scene of the Sahara Desert photographed by a photographer went viral on the Internet. This photo taken on February 22nd, 19 shows that the red sand dunes are covered with white snow, which brings the feeling of ice and fire. This is the second snowfall recorded in the hottest place in the world. The last snowfall in the Sahara desert was in February 1979, when the snow scene only lasted for half an hour. This time, the heavy snow lasted all day!

Snow fell in the Sahara desert, reaching a record high temperature of 58℃. It is understood that desert snowfall exists, but it is extremely rare. "Snowfall in the Sahara is even rarer. Violent westerly wind fluctuations let us see snow in the hottest place in the world! " Professor Wu Xiuchen of Peking University said that it will rain in the desert, but the rain in the desert is fleeting, usually in the form of showers. According to statistics, the annual precipitation in the Sahara desert does not exceed 10 mm, and the rainfall is very small. "But since it can rain, it will snow. It's just snowing in the desert area, which is a small probability event. "

Wu Xiuchen graduated from Peking University with a Ph.D. in physical geography, and later worked as a postdoctoral fellow in the Climate and Environmental Science Laboratory of the French National Scientific Research Center. He introduced that snow needs two key factors: one is enough water vapor, and the other is low enough temperature. The difference between snow and rain depends on the temperature at high altitude. If the temperature at high altitude is low enough, snow can form.

The Sahara Desert covers an area of about 9.32 million square kilometers, located on both sides of the Tropic of Cancer, and is controlled alternately by subtropical high and trade winds all the year round. Wu Xiuchen introduced that the climate here is high temperature, dry and little rain, and the four seasons are not obvious. There are three main reasons: the dry northeast trade wind blows from the inland of Asia, making it difficult to form precipitation, making the Sahara region more arid; The coastline of North Africa is relatively straight, and the Ethiopian plateau on the east side blocks the humid airflow from the ocean, making the vast inland areas unable to be affected by ocean water vapor; The canary cold current passes through the west coast of North Africa, cooling and dehumidifying, and even the coast is endless barren land. These reasons have caused a single tropical desert climate here.

Wu Xiuchen said that the climate of the Sahara desert is controlled by the transition from the north to the south of the trade wind belt, and many extreme phenomena often occur. "Snowfall in the mountainous areas of the Sahara is possible, but snow on sand dunes is extremely rare." The snowfall in the northern Sahara is closely related to the strong cold advection behind the trough caused by the anomaly of the West Asian trough. Combined with the anomaly of the subtropical high in the North Indian Ocean, the water vapor at the edge of the subtropical high is brought, and the flow field is also the key place affected by the northwest Mediterranean wind. So the place where it snows is in the hinterland of Atlas, not in the center of Sahara.

(Source: Network)