Obstructed by the Tibetan Plateau, summer low-level westerly is split into two branches, which causes northern and western moisture flows around the plateau respectively, thus exerts a significant influence on East Asian climate. By Utilizing different reanalysis data and performing various statistical methods, this project firstly analyze spatial-temporal variabilities (including interannual and decadal scales) of two branches of moisture flow (hereafter, NBMF for northern branch of moisture flow and WBMF for western branch of moisture flow), so as to recognize their multi-scale characteristics fully; secondly investigate combined downstream effects of NBMF and WBMF multi-scale variabilities on anomalous summer rainfall patterns in East Asia; finally stress time-lagged evolution of land-atmosphere coupled system associated with NBMF and WBMF, such as thermal and snow cover condition of Tibetan Plateau. The successful development of this project will disclose some key physical processes about impact of Tibetan Plateau on regional climate, and build the conceptual model about the downstream effect linked with mid-latitude westerly, Tibetan Plateau and East Asian rainfall anomaly，which give a great push for a reliable prediction of East Asian summer climate.