Analysis of a Sustained Torrential Rainstorm Events in Sichuan Basin Induced by Plateau Vortex Moving Eastward

Using the conventional observation data，precipitation data from automatic stations，NCEP reanalysis data(1°×1°) from NCEP/NCAR center and FY2E satellite TBB，a case of heavy rainstorm in Sichuan basin caused by plateau vortex shear moving eastward from 15 to 19 July 2013 was analyzed．Results are as follows:The heavy rainfall occurs on the edge of northwest of the subtropical high，which is the unstable region，and the proliferation of the low－level cold air moving southward is the key factor in triggering heavy rainfall occurs．The strongest intensity of heavy rainstorm appears in the mature stage of development of the MCS system，and so dose the 1h maximum precipitation when the coldest cloud increases to the top size．The horizontal distribution of negative wet z－helicity at low－level correspond well with the heavy rainfall center of the same period of time．In the vertical distribution of the rainfall area，the favorable dynamic structure of the positive vorticity with water vapor convergence rotation in the low－level and negative vorticity with moisture divergence rotation in the high－level contribute to trigger the torrential rain．