Numerical Simulation And Diagnostic Analysis Of Meiyu Front Rainstorms In 2005

The average circulation characteristics during Meiyu period are analyzed with NCEP objective analysis data and different non-conventional objective data. It is revealed that the variations of lower level south-west jet in Meiyu are close related to advance, retreat and remain of rain band. At the same time, the variations play an important part in formation of Meiyu front and heavy rain; By using conventional data, the strongest rainfall in Meiyu is studied. Using synoptic diagnostic methods, we get some conclusions about vertical and horizontal structure characters of typical Meiyu Front: the wind of Meiyu front constitutes by south-west monsoon coming from south and east air current coming from north, and Meiyu front is almost in the middle of east jet and west jet where the potential temperature is almost vertical and has lots of energy in the lower level. The diagnostic analyses show that the heavy rain is produced by trough, shear line and vortex from Yangtze River to Sichuan province. The mesoscale numerical mode MM5 was used to simulate this heavy rain. Apparent heat sources,apparent moisture sink,Modified wet Q vector and MPV are researched by using simulation results. The diagnoses play a good role in forecasting mesoscale rainfall and rain band. The grapth display system of mesoscale diagnostic variables is software that can output different diagnostic variables' graph in weather diagnosis. With the help of this software, we can get easily diagnostic variables' graph in different times and different levels. Users will understand the dynamic process from different perspective, open out the mesoscale structure's characters and the physical meaning, and avoid repeated working. The terrain sensitivity test and vapor condensation latent heating test were done for understanding the function of terrain and vapor condensation latent heating, Through tests we can found that the vortex of north of Mountain Dabie have certain influence on the location and intensity of rainfall, meanwhile, condensation latent heating play an important part for the happiness and the development of mesoscale system.