The Diagnostic Analysis And Numerical Simulation For The Heavy Rain Event In Guizhou

During 17-20, June in 2002, there occurred an infrequent heavy rain in the north and mid-part of Guizhou , and on the common boundary of guizhou,Hunan and Chongqin, resulting from the united effects of trough to the east of Plateau, low shear and quasi-stationary front on surface, which results in serious disaster.A rainstorm process is simulated in Guizhou during 18-20, June in 2002, based on meso-scale numerical model MM5 (V3). With the basic physical parameters from the modeled output, the potential equivalent temperature and vertical velocity are analyzed, and calculation of the helicity and the barotropic and baroclinic moist potential vorticity(MPV) are made. The diagnosis results are as follows:The center of rainstorm is adjacent to the center of the maximum vertical velocity;the south and north meridional-vertical circulations are significant to the in-and out-flow on the lower and upper level, respectively. The changes of the helicity is a favorable index for the evolution of the rainstorm intensity. The rainstorm area is to the dense part of helicity isograms;Both the dry and moist potential( PV) can well present the features of the weather systems. The dry PV reflect both the cold and warm air flow activities, It is favorable for causing the heavy rainstorm when the upper tropospheric dry PV tends downward to lower- levels and vice versa for the lower- level troposheric dry PV.But once the PV weakens in upper-and lower- levels the precipitations will be ended soon. The heavy rainfall over Guizhou start, get stronger and weaker with the high value area' s formation, strengthen and perish of MPV1" funnel" at 500hPa. it is also found that plus MPV zone just over minus one will make for the taking place and development of the heavy rainfall. The plus MPV zone at 500hpa is in accordance with the convective rainfall area, as well as the variable strength.