Abstract:Based on the rainfall data from 722 stations in China, NCEP/NCAR reanalysis data, and the daily rainfall data from 7 stations in Qingdao from January 1961 to December 2011, the precipitation phases of flood season in Qingdao and the corresponding climatic circulation background are analyzed. The results show that 5 stages could be identified in the Qingdao summer flood season, including the initial stage of the main rainy season (29 June to 3 July), the stage of the Yellow River Huaihe River rainy season (9-25 July), the stage of North China rainy season (27 July to 6 August), the stage of tropical depression (11-20 August), and the end stage of the main rainy season (29 August to 4 September), respectively. In each stage, the corresponding climatic circulation background and the impact systems are relatively stable. The stage of the Yellow River Huaihe River rainy season and the stage of tropical depression are two major precipitation stages with strong intensity and longer duration. The main reasons for the formation of the stages in flood season in Qingdao are the seasonal movement of subtropical high and the circulation configuration in high and low levels. The circulation between different stages shows clearly the phenomenon of abrupt changes.