Abstract:Based on the daily precipitation data from 56 stations in Yangtze River Basin in summer, NCEP/NCAR reanalysis data, sea surface temperature data from Hadley center, the spatio-temporal variation of precipitation frequency for different categories in Yangtze River Basin and associated atmospheric and oceanic pattern were analyzed. More details are as follows:(1) There is a trend that total rain days happened more frequently in Yangtze River Basin in summer in recent 53 years, while the heavy rainfall frequency ratio of total rainfall frequency was increasing, and light rainfall frequency ratio of total rainfall frequency was decreasing. (2) Spatiotemporal variation of precipitation frequency for different categories in Yangtze River Basin and associated atmospheric and oceanic pattern are different from each other. In the heavy rainfall active period,early sea surface temperature in spring distributes as east-pattern El Nino, circulation is much stronger, Pacific-Japan teleconnection pattern shows "+-+" form at 500 hPa geopotential height, and the western Pacific subtropical high is stronger, moreover, the position of western Pacific subtropical high is more westward and southward. Dual-blocking pattern presents in Ural mountain and Okhotsk sea. Australian high in the Southern Hemisphere, cross-equatorial flow, westerly jet round 30°N at 200 hPa geopotential height are much more stronger, and presents cyclonic-anticyclone-cyclonic form at 850 hPa wind field.