2008年“7.02”滇中大暴雨的成因诊断与数值模拟

Diagnostic Analysis and Mesoscale Numerical Simulation of Extremely Heavy Rainstorm on 2 July 2008 in Middle Yunnan

利用常规观测、NCEP 1°×1°再分析资料、云图、多普勒雷达回波和WRF模式对2008年7月2日滇中大暴雨进行成因诊断和数值模拟。结果表明:对流层高层的干侵入和中低层冷、暖平流交汇诱发副热带高压和滇缅高压间辐合低涡迅猛发展成强中尺度对流辐合体,加上中低层来自孟加拉湾的丰富水汽输送和中低层强水汽辐合共同引发此次大暴雨。过程中,垂直螺旋度贡献主要在中层;干位涡呈现出对流层顶强正高位涡,300 hPa以下为次正高位涡,两者之间为负区的柱状分布特征,次正高位涡强中心有向下层延伸特征。WRF较好地模拟了整个大暴雨过程中强降水主体时段和大暴雨落区特点,最大对流有效位能变化趋势对强降水有较好预示作用,模拟方案在积分30小时内效果较好。

Using the conventional observed data,the NCEP 1°×1°grid point material,cloud-images and CINRAD-CC Doppler weather radar data,and the mesoscale numerical model WRF,an extremely heavy rainstorm occurring in the middle of Yunnan Province on 2 July 2008 has been diagnosed and simulated. The result shows that the heavy rain is caused by the dry intrusion from the upper troposphere,cold and warm advection confluence in the low middle layer and abundant vapors from the Bay of Bengal.In this extremely heavy rain process,the most effects of vertical helix are in the middle layer,supreme positive potential vorticity（PV） exists on the tropopause,the sub-supreme positive PV is under 300 hPa,and between the two layers present columnar distributing characteristics.Meanwhile,the sub-supreme positive PV can affect its lower layers.The simulated rain and reflectivity distributions by WRF mesoscale numerical model show that the characteristic of rain belt and generant time in Yunnan Province are well reproduced. The change trend of simulated maximum convective available potential energy（CAPE） can well indicate the rain occurrence.The simulation result is better within 30 hours.