Why is there a summer drought in the middle and lower reaches of the Yangtze River?

Because from the middle of July to the middle of August. At this time, the stationary front of Meiyu has moved to the middle and lower reaches of the Yellow River and northeast China in early July, and the middle and lower reaches of the Yangtze River are controlled by the "subtropical high", forming an anticyclone weather, which is dominated by underflow air, with long sunshine, strong solar radiation, high temperature and strong evaporation. Crops grow fast, and farmland needs a lot of water.

However, due to the single air mass, except for thunderstorms in some areas, there is no big rain area, and generally there is dry and hot summer weather, so it is called "summer drought". In this season, the afternoon temperature in the middle and lower reaches of the Yangtze River generally reaches 33 ~ 35℃, and the high temperature as high as 43 ~ 45℃ appears in some places. It mainly occurs in the Yangtze River basin and the south of the Yangtze River, especially in Hubei, Hunan, Jiangxi, Jiangsu, Anhui and other provinces.

When the subtropical high in the western Pacific is controlled and typhoon activity is low, severe drought is prone to occur, and the precipitation is obviously less than the multi-year average. Generally from mid-July to mid-August. (The dog days begin in summer and last for about 10 days after July 12 every year. )

Extended data:

Summer drought characteristics

Summer drought is characterized by strong solar radiation, high temperature, low humidity and large evaporation and transpiration, which is the hottest period in a year. Under the control of the western Pacific subtropical high, the Yangtze River basin in China is sunny and hot with little rain, and the summer drought occurs frequently, up to 50%. In other areas, there are droughts in some years. ?

Summer is a period of vigorous crop growth, although summer drought is not as frequent as spring drought; However, the damage to crops is generally heavier than that in spring drought, so there is an agricultural proverb that "there is no drought in spring, and the drought in summer is halved".

Summer drought is not only related to the growth of crops in that year, but also determines the reservoir capacity and the formation of soil moisture in that year, which has an important impact on the growth and yield of winter wheat and spring sowing crops in the coming year. Drought in the middle and lower reaches of the Yangtze River and the eastern Sichuan Basin in midsummer.

Summer drought occurs after the meiyu period, usually in the dog days from mid-July to mid-August. During the summer drought, it is hot and muggy, sunny and rainy, with strong evaporation and severe drought. The average temperature in July can reach 28-3 1℃, such as 28.6℃ in Chongqing, 29.0℃ in Hankou and 28.2℃ in Nanjing, which is known as the "three furnaces" in the Yangtze River basin.

Baidu encyclopedia-summer drought