The Mechanism Study And The Numerical Simulation Of Heavy Rainfall Process In Henan Caused By Typhoon "Haitang"

Based on the conventional metearological observation data, the 714CINRAD Doppler radar data in Zhenzhou and 1°×1°NCEP reanalysisgrided data, the heavy rainfall, which was caused by the TyphoonHaitang in Henan from 20 to 23 July 2005, is diagnostic analyzedpreliminaruly. It is found that the interaction between the southeasterlyjet between the south of subtropical high and the peripheral typhoon lowpressure, typhoon inversion trough and cool air is the direct influencingsystem, persist fluenceing of precipitation echo next surface mesoscaleconvergence line made important effect on the heary rainstorm forming,strong southeasterly warm-wet air current afforded abundance watervapour and instability energy, and the pumping caused by convergencein low level and dirvergence in high level is the dynamic condition of therainfall enhancing. By isentropic potential vorticity analysis, themechanism of this typhoon rainstrom is revealed that typhoon had a highpotential vorticity structure and heavy rainfall ocurred in the south ofsoutheasterly jet in its northeast. When typhoon arrived at the area inhigh latitude, precipitation inensity enhanced obviously if cool air withhigh potential vorticity invaded. And the southward moving of westerlyjet in high level benefited the southward transportaion of high potential vorticity area which advanced intensification of heavy rainfall. Based onmoistrue Q-vector analysis, it is found that convergence area, wheremoistrue Q-vector analysis divergence was not greater than -20×10^-15hPa^-1·s^-3, had a good designating singification for torrentialrain area infurther. The further rainfall would remarldy reduce in the area withstrong convergence in low level and strong dirvergence in middle level.And the long lasting of convectional stability stratification could delaythe beginning time of the heavy rainfall.The heavy rainstrom process on 22 Jul 2005 was simulated usingnonhydrostastic mesoscale numerical model MM5(V3.6), and the resultsshowed that, the model had a good capability to simulating the wholeprocess of the mesocale system forming and developing, and thesimulative precipitation was close to the observation. Deep humid leveland unstable stratification had formed before the heavy rainfall tookplace. Positive and negative vorticity columns all appearing in high andlow level, coupling structure of divergence columns, allocation ofcoupling structure and strenuous ascending motion, leaded to fast releaseof instability energy and rainstorm ultimately.