Sand and dust: I left. I am back again... Netizens: Is this "returning sand"?

Starting in the evening of April 12

Beijing's air quality is off the charts again

#Beijing sandstorm#

#回锅沙要来了# and other topics

Quickly became a hot search

Sparked heated discussion among netizens

The sandstorm had been blown south of the Yangtze River by strong winds.

Why did Beijing’s air quality exceed the limit again in such a short period of time?

Wei Ke, associate researcher at the Institute of Atmospheric Physics, Chinese Academy of Sciences

Let me give you some general knowledge!

Why does the dust go away and come back again? Is it “returning sand”?

Wei Ke said that this was not a new dust storm, but a return of dust storms from the south. Netizens called this dust storm "returning sand", which is very descriptive. The weather system that caused the storm is called backflow weather. Backflow weather is a common weather process in North China.

How is backflow weather formed?

Wei Ke said that the formation of backflow weather is closely related to the continental cold high pressure. The cold high pressure is generally an anticyclonic system with a clockwise circulation. Therefore, the wind is northerly on the east side of the cold high pressure, the wind is southerly on the west side of the cold high pressure, and the wind is easterly on the south side of the cold high pressure.

The southerly or easterly winds of the backflow weather will transport pollutants on the North China Plain from east to west or from south to north, thereby accumulating along the Taihang Mountains and Yanshan Mountains, forming relatively serious polluted weather.

Wei Ke explained that when the cold high pressure moves from west to east through North China, the first thing that affects North China is the northerly wind from the east, which easily blows up dust from Mongolia and the northern sand source areas of my country, and affects my country from north to south along the wind. As the cold high pressure moves eastward to the sea, North China is generally in the western part of the cold high pressure, and the wind direction turns to southerly wind, thus blowing the dust blown to the south back.

Experts advise

A new round of sandstorms is on the way

Please prepare for protection

Source: Science and Technology Daily