一次陕北暴雨过程的数值模拟与诊断研究

应用WRF中尺度模式对陕西省榆林市2006年9月20日21:00~21日11:00的一次暴雨过程进行数值模拟,通过降水实况和环流形势的对比,可以认为模拟的结果较好地复制了这次陕北大暴雨过程;应用模式输出的基本物理量分析了垂直速度和相对湿度,并计算分析了干位涡、湿位涡正压、斜压项以及扰动位涡,揭示了这次暴雨产生的机理。结果表明,湿度场和垂直上升运动的相互耦合是此次暴雨发生发展和维持的动力机制;在暴雨发展的峰值时,干位涡的大值中心对应着暴雨的大值中心,干位涡对暴雨的预报有很好的指示意义;MPV1高值与对流稳定的冷空气相联系,较小的MPV1正值或负值区域与对流不稳定或对流稳定度低的暖湿空气相联系;中低层正值位涡扰动的存在是暴雨发生发展的重要条件。

A Diagnosis and Simulation Study of A Strong Heavy Rainfall in Northern Shaanxi

A heavy rainstorm during Sep 20th 21：00 - 21st 11：00, 2006 is numerical simulated by meso-scale mode of WRF. Compared raining reality to circumfluence, it can be considered that this process is better provided by the result of simulation. Vorticity and relative humidity is an- alyzed with the basic physical element of mode output. Potential vorticity, humidity potential vorticity barotropic, baroclinic item and disturbance potential voriticity are calculated. It finds out the mechanism of the rainstorm. The diagnostic analysis shows that the coupling of hmnidity field and vertical rising movement is the dynamical mechanism that makes the rainstorm occur and last. At the top of the storm, the center of Potential vorticity is in the center of the storm, so it shows that potential vorticity is meaning a lot to the storm forecast. Tile high of MPV1 is isolated with the convective stable cold air. The smaller positive or negative value area is isolated with the unstable or less convective stable warm air. The existence of middle-low positive potential voriticity disturbance is the important condition of the rainstorm development.