Subseasonal Changes and Causes of Trends of Extreme Precipitation Frequency During June and July in Central Eastern China

Abstract Long‐term changes of extreme precipitation have been a big concern in various regions. Previous studies are mostly concerned with trends of seasonal frequency and intensity of extreme precipitation and interpret those trends based on long‐term changes in seasonal mean moisture. Present study analyzes trends of extreme precipitation frequency in sub‐periods of the rainy season (June and July) in central eastern China and roles of atmospheric circulation changes. It is found that the trends of extreme precipitation frequency have prominent subseasonal changes in central eastern China. The frequency of extreme precipitation displays an increasing trend in early June and early and middle July, but a decreasing trend in middle and late June and late July. The trends of extreme precipitation frequency are attributed to those of corresponding atmospheric circulation patterns in sub‐periods of the rainy season. Increasing (decreasing) trends of extreme precipitation frequency are associated with increasing (decreasing) lower‐level southwesterly winds over southeastern China, westward extending (eastward retreating) western North Pacific subtropical high and strengthening (weakening) East Asian trough. The mean atmospheric circulation trends play a role in the subseasonal changes in the trends of extreme precipitation frequency in central eastern China. The change in the mean moisture availability cannot explain subseasonal changes in the trends of extreme precipitation frequency. Present study suggests the necessity of analyzing extreme precipitation trends and roles of atmospheric circulation trends during sub‐periods of seasons.