Primary Research &. Analysis On The Dynamical Mechansim Of Heavy Rain Over Changjiang-Huaihe River Basin During The Meiyu Period

Based on NCEP and other observational datasets, two severe heavy rainfalls process occurred over Changjiang-Huaihe River basin during July, 2003 were primary investigated. The first diagnostic analyses show that the heavy rainfalls are produced together by vortex, shear line and upper and lower jets, Meiyu front. The condition of high energy, saturation, potential instability is propitious to the form and maintenance of heavy rainfall. The result of numerical simulation by MM5 model shows that heavy .rainfall has close relation with meso-scale vortex pole and strong convection. Further research shows that the form of meso-scale vortex pole is relate to the coupling of upper and lower jet streams, and dry intrusion. Potential instability that exists with conditional symmetrical stability make the vertical ascend movement inθe big value area and slope ascend movement in θe surface (Meiyu front area) produce and maintain. Diagnoses of apparent heat source, apparent moist sink and helicity show that the severe heavy rainfall is related with them closely. Use radar and satellite data to improve initial humidity field and four dimensional variational data assimilation to improve initial wind field, and simulate it with MM5, which has improved the simulation ability of Meiyu heavy rainfall.