The weather system that causes the dry weather in summer in the Yangtze River basin in China is

B subtropical high. Generally from mid-July to mid-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. Generally, when the subtropical high in the western Pacific is controlled and typhoon activity is low, severe drought is prone to occur. 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. )