Diagnostic Analysis on the Dynamic Mechanisms of Occurrence and Maintenance of Mesoscale System in a Heavy Rain

With 1°×1° (longitude×latitude) NCEP/NCAR reanalysis data, surface observed hourly precipitation and TRMM ancillary data products, an analysis is made of mesoscale convective systems triggering heavy rain in southern Guizhou province during 8-9 June 2009 to study the role of barotropic non-equilibrium force and baroclinic coupling forces between dynamic and thermodynamic fields at the stage of occurrence and maintenance of heavy rain.The results show that:the large area rainfall during 8-9 is produced by mesoscale convective system.Moisture transporting to the heavy rain area from the South China Sea is main moisture source supplying severe precipitation, and it also brings enough energy to the south of Guizhou.The barotropic non-equilibrium force's negative value region is highly correlated with rainfall at the starting time for precipitation, and it is the dynamic mechanism of heavy rainfall maintenance.The baroclinic coupling forces between dynamic and thermodynamic is well corresponding with rainfall and the mesoscale convective system during the stage of heavy rainfall maintenance, especially when the area atmosphere's stratification is neutral or little stability.