Diagnostic Analysis of the Heavy Rain Occurrence and Maintenance Dynamic Mechanisms by Coupling Forces between Dynamic and Thermodynamic Fields

Using a new type of divergence equation which is derived by Chen Zhongming (2008) and the NCEP/NCAR1°×1° reanalysis data to analyze the Barotropic non-equilibrium force and the Baroclinic coupling forces at the process, the persistent heavy rain in Sichuan and Chongqing during 16-20, July, 2007, compared with the 1-hour and 6-hour observed precipitation and TRMM ancillary data products.The results show that:i) The heavy rainfall mainly happen at the stage when the area atmosphere's stratification is neutral or little unstability stratification.ii) The barotropic non-equilibrium force has great important to the occurrence of heavy rain, it is the dynamic mechanism of heavy rainfall occurrence, at the beginning or weaken of the heavy rain, the barotropic non-equilibrium force fields and the precipitation center are at the same area.iii) At the stage of the heavy rain maintenance, the baroclinic coupling forces between dynamic and thermodynamic fields are corresponding with the area of the heavy precipitation, it is the dynamic mechanism of heavy rainfall maintenance.iv) The change of the divergence evolvement which led by the barotropic nonequilibrium force and the baroclinic coupling forces is consistent with the area, the strength and the position of the heavy rain which happens 6 hours latter.The barotropic non-equilibrium force and the baroclinic coupling forces between dynamic and thermodynamic may instruct the prediction of the heavy rain effectively.