切变线暴雨过程中湿位涡的中尺度时空特征

Temporal and Spatial Mesoscale Characteristics of Moisture Potential Vorticity of Shear Line Heavy Rain

利用中尺度数值预报模式MM5V3.6,对2005年9月19—21日发生在山东中南部的区域性切变线暴雨天气过程进行了数值模拟。并用高时空分辨率的模式输出资料,对此次暴雨过程的湿位涡场特征进行了诊断分析。结果表明:θse面陡立易导致湿斜压涡度的发展,形成θse陡峭密集区,密集区内容易发生暴雨。通过湿位涡的分析,揭示了暴雨过程中湿位涡的中尺度演变特征和空间结构,表明切变线暴雨的发生发展与湿位涡的时空演变有很好的联系。暴雨主要出现在850hPa的ζMPV1负值区和ζMPV2正值区等值线密集区附近,降水中心位于ζMPV1负值中心前部对流不稳定区中。

By using the mesoscale numerical model MM5 V3.6, a successful simulation is made for heavy rain event in the central and southern parts of Shandong Province on September 19 - 21, 2005. And the moist potential vorticity of the heavy rain is analyzed by using high resolution simulation result. The results indicate that the stiff moist isentope.s excite the development of moist slantwise vorticity and occurrence of heavy rain, A diagnosis of moisture potential vorticity is made to show its temporal and spatial mesoscale characteristics. The results show that the development of heavy rain is closely related to the temporal and spatial variations of moisture potential vorticity. The heavy rain occurs in the isoline dense section of the negative MPV1 and positive MPV2, and the rain center lies in the convective instable section in the front of the negative MPV1 center at 850hPa.