2000年7月西南涡暴雨过程的分析和数值模拟

Analyses and Numerical Simulations of Southwest Vortex Rainstorm Processes in July 2000

对2000年7月1～8日西南涡暴雨过程进行了大尺度分析,并利用中尺度暴雨模式MRM1对这次过程进行了数值模拟,结果表明,这次西南涡暴雨过程分为两个阶段,分别对应着两次冷空气南下。暖切变线的南北摆动是发生大暴雨的一个重要原因,而西南急流核的向北传播导致雨区向北传播。模式成功地模拟出了中-α尺度的低涡、切变线,沿暖切变线的强烈倾斜上升气流、中尺度正涡度以及水汽通量散度辐合柱状结构,这些对暴雨的发生提供了动力和水汽条件;而沿低空急流轴的狭长暖湿舌,其北部的干冷区构成的南北向能量锋区,以及较强的中低空不稳定层结是这次暴雨持续发生的重要条件。

The large scale weather system of the southwest vortex rainstorm process during 1～8 July 2000 is analyzed. Also the numerical simulation of this process is conducted by a mesoscale model(MRM1). It is shown that the rainstorm process of southwest vortex is divided into two stages, corresponding to two cold air processes of moving southward respectively. Latitudinal fluctuation of warm shear line is an important factor for rainstorm. Northward propagation of southwest jet cores causes the rain area moving northward. The meso-α scale vortex and shear line are successfully simulated. Its intense inclined rising air current, mesoscale columnar structure of positive vorticity, as well as the convergence moisture flux divergence provide for dynamical and moisture conditions of the heavy rainstorm, while the energy frontal zone of the south-north orientation, the long and narrow warm moisture tongue along low-level jet axes, the rather strong middle and low level unstable stratifications are important condition of this persistent rainstorm.