Analyses on "2003.8.28" Heavy Rain in the Upper Reach of Yangtze River

Based on the T213 objective analysis data, the causes of heavy rain in Sichuan from 28 August to 1 September of 2003 have been analyzed. The results show that the building of south low-level jet provided abundant vopour transfer and convergence for the heavy rain. The cold advection in low- and-mid levels and the wind of low-level jet are and trigger mechanism of the heavy rain process. South-West (SW) vortex occurred after heavy rain. The pumping effect resulted from low-level convergence and upper-level divergence caused stronger upward current, the coupling of convergence region with positive vorticity make SW vortex to develop and maintain, leading to more rainfall in Sichuan Basin.