Abstract: | Selecting appropriate Asian summer monsoon indices and classifying them, combined with the summer precipitation data in the middle reaches of the Yangtze River from 1979 to 2020, analyzed the characteristics of summer atmospheric circulation and precipitation in the middle reaches of the Yangtze River during the abnormal summer monsoon years. The main conclusions are as follows: (1) Both types of summer monsoon indexes are negatively correlated with summer precipitation in the middle reaches of the Yangtze River, and the correlation between the second type of summer monsoon indexes and summer rainfall in the middle reaches of the Yangtze River is more significant, so the second type is selected The summer monsoon index determines the strong and weak summer monsoon years. (2) The precipitation in the middle reaches of the Yangtze River has the characteristics of low-frequency oscillation. In the strong summer monsoon year and the weak summer monsoon year, the main period of the oscillation is 32-64 days. (3) The precipitation difference between strong and weak summer monsoon years mainly depends on the strength of the West Pacific Subtropical High and the water vapor transport of the southerly monsoon. |