华北地区一次积层混合云降水过程的数值模拟分析

Numerical Simulation Study of a Convective Stratiform Mixed Cloud Precipitation Process over North China

利用新一代非静力平衡中尺度数值模式WRF模拟,从动力、热力机制和微物理过程等方面分析了2009年4月30日08:00～5月2日02:00发生在华北地区的一次积层混合云降水过程。结果表明,水汽辐合主要是由西南暖湿气流提供,且西南暖湿气流区域的大气层结始终处于对流不稳定状态,为华北地区对流的发展提供了热力机构基础,而均匀上升气流场中的波动导致了对流云镶嵌其中;降水云系中冷云降水机制与暖云降水机制共存,主要降水由对流云提供,而播撒-供应机制可能是导致此次积层混合云降水的主要原因。

By using the WRF model numerical simulation, a convective stratiform mixed cloud precipitation process occurred in North China from 08：00 on April 30 to 02：00 on May 2,2009 was analyzed from its dynamic and thermal mechanisms and micro physical processes. The results showed that the moisture convergence was mainly caused by warm-moist airflow from southwest, and the atmospheric stratification of warm -moist airflow area was in an unsteady state all the time ,providing thermal-structure base for the development of the convection above North China ,while the dramatic fluctuations of updraft led to embedded convective clouds. The cold and warm cloud precipitation mechanisms coexisted in the pre- cipitation nephsystem, and the rainfall was mainly supplied by the convective cloud, and the ＂seeder -feeder＂ mechanism may be the main reason of the convective stratiform mixed cloud precipitation.