一次激发积层混合云降水的数值模拟

Numerical Simulation of the Complex of the Stratiform and Embedded Convective Cloud Precipitation

利用WRFARW中尺度数值模式对2007年7月29日山西南部喇叭口地形造成的一次积层混合云系降水进行模拟。通过分析云系中不同水相粒子的分布，了解积层混合云系的微物理特征和动力特征，最后对地形激发的积层混合云系降水机制进行探讨。结果表明：特殊地形所激发的meso—β积层混合云系是造成特大暴雨的直接系统；高层层状云与中低层的积雨云相互粘连跨接，自上而下依次为冰晶区、冰晶和过冷云滴共存区和云水区，雨水大值中心、云水大值中心和冰晶大值中心相互对应，存在“播撒-供给”机制；动力场上，低层对流云中有强上升气流，高层层状云中在上升气流旁侧有较明显的下沉气流，低层存在强辐合，中高层存在强辐散，此种配置有利于维持云系的发展。对流云与层状云的相互作用使对流发展旺盛，产生极端强降水。研究初步概括出夏季地形激发的积层混合云降水的概念模型：天气系统提供低层辐合、高层辐散的环流背景，地形辐合、山脉抬升提供中尺度对流云团的触发、加强条件，Bergeron效应是冷云降水的关键过程，“播撒-供给机制”是层积混合降水的主要降水机制。

On July 29 2007, a torrential rain event occurred in Yuanqu, in the south of Shanxi province, and this event was regarded as a typical trumpet-shaped orographic complex of the Stratiform and Embedded Convective Cloud Precipitation. In order to study the orographic effect in the event, numerical simulation is conducted with the Weather Research and Forecast Model （WRF ARW）. Cloud microphysical characteristics and dynamic characteristics are studied by analyzing elements of cloud. The results indicate that： the meso- β Stratiform clouds with convective clouds excited by special terrain was the direct system of the rain storm. The stratiform clouds and convective clouds connect each other, and mix horizontally. The locations of maxima of rain water, ice crystal and cloud water content are correspondent vertically, and Seeder-feeder mechanism exists. Vertical velocity is accessional in the convective clouds, and downdraft is on the side of the convective clouds at high altitudes. Convergence can be found at low altitudes, while divergence can be found at high altitudes. This configuration is conductive to maintaining the development of cloud .