Observational Analysis And Numerical Simulation Of Heavy Rainfall Over Huaihe Valley During 3～4 July 2003

Conventional and high resolution observation data such as satellite, radar and the Surface Automatic Station data are used to analysis the development Characteristics of MCSs Associated with rainmass activity for an heavy rainfall over Huaihe Valley during 3~4 July 2003. The results showed that the development of meso-β-scale convective system in mei-yu front meso-α-scale cloud system was the direct reason of heavy rainfall by the favourable background of large-scale circulation. The strength and locations of heavy rainfall were closely related with the activity of meso-β-scale disturbances. There were three rainmass active periods corresponding to three peak value of rainfall intensity within the whole process, and their lifetime were dissimilar. The first and the third rainmass activity are caused by the continuous affects of some massive dispersive meso-β-scale convective complex, and that the second rainmass activity was related to the rapid development of about 100km-long meso-β-scale convergence zone near the surface. The lifetime of meso-β-scale convective cloud cluster may not be the same as rainmass. One living process may be corresponding to either one meso-β-scale convective cloud cluster activity or multiple activities.The dominant effects of heavy rainfall events are the convective complex and some strongconvective monomer which echoes were from 40 to 60dBZ. The echo intensities anddevelopmental height had positive correlation to the intensity of surface precipitation. Then, numerical simulation is made on the heavy-hard rainfall over Huaihe Valleyusing the PSU/NCAR MM5 model. We find that the MM5 model do quite well insimulating and could provide the high-resolution data to diagnose.Meso-a-scale and Meso-P-scale about 100km-long convective systems can bereflected by the MM5 model. But the model has limit of meso-β(γ)-scale which havesmall scale and strong development.Finally, that the direct reason of the second rainmass activity is the rapiddevelopment of about 100km-long meso-β-scale convergence zone near the surface isvalidated by the high-resolution data provided by the MM5 model, the mechanism andstructure of mesoscale systems are studied by conducting diagnostic analysis, theory ofdynamics and numerical simulation.