河南省春季一次层状云降水云系结构和降水机制的数值模拟

Numerical Simulation of Cloud System Structure and Precipitation Mechanism of Stratiform Precipitation in Spring of Henan Province

利用PSU/NCAR的MM5中的双参数显式云物理方案,模拟了2007年河南省春季一次层状云降水过程,模拟结果显示,降雨主要落区和强度与观测一致,24 h降雨预报的TS评分较高。模式输出的雷达反射率与郑州站雷达RHI回波相比较,模拟的回波结构基本符合层状云回波特征,存在零度层亮带。在成功降水模拟的基础上,分析了云系不同部位结构特征和粒子质量通量分布,发现雨水的形成在不同部位依靠不同的过程。郑州站云的垂直结构和降水微物理过程研究表明,降水机制符合"播种—供给"机制,降水形成主要依靠雪的融化和暖云微物理过程,暖云对整层降水起主要作用,暖云微物理过程是形成降水的更有效方式。

A stratiform precipitation of Henan province in spring of 2007 is simulated by using the PSU/NCAR mesoseale model （MM5） with double-moment explicit microphysic scheme. The simulated results show that the predicted precipitation location and strength agree fairly well compared to observation and the threat score of 24 h precipitation forecasting is high. The output result of radar reflectivity in the model is agreed with the radar echo on the RHI display at Zhengzhou station, which has the characteristic of stratiform radar echo and exists 0℃ isotherm bright band. On the basis of success precipitation simulation, the cloud system vertical structure and mass flux at different locations is analyzed. The rain forma- tion at different regions depends on various processes. The results of cloud vertical structure and precipitation microphysics process at Zhengzhou station showed the precipitation formation mechanism is the ＂seeder-feeder＂ mechanism. The dominant microphysical process for precipitation is the snow melting below the freezing-level and warm cloud processes. Warm cloud is the main contribution for the integrated precipitation and warm cloud microphysical process is a more efficient way of forming precipitation than the cold cloud process.