单双参云微物理方案对强降水过程中云宏微观特征模拟的对比分析

Comparative analysis of single-moment and double-moment microphysics schemes in WRF on the heavy precipitation process of the macroscale and microscale characteristics of the cloud

将WRF3.9模式的16种云微物理方案分为单参、双参两组,分别对2016年6月30日—7月4日江淮流域的一次强降水过程进行模拟。首先利用逐小时观测降水对各组模拟降水进行评估,在此基础上利用FY-2G和CALIPSO云产品数据分别评估不同方案对降水过程中总云量、云垂直结构云水含量等宏微观特征的模拟性能。结果表明:选用不同的云微物理参数化方案均能较好地模拟出该次过程的雨带位置和中心降水强度,但不同方案对云宏微观特征的模拟结果有显著差异。分析两组试验对总云量的模拟结果发现,单参方案组除Kessler暖云方案对冰云过程描述不足导致模拟的总云量显著偏高外,其他单参方案和所有双参方案均能模拟出强降水过程中总云量的时空演变特征。从云覆盖率和云水含量的垂直分布特征来看,单参方案组对600 hPa以下中低层暖云的模拟稳定性整体略优于双参方案组;而对200~500 hPa的冰相云模拟结果相反,双参方案组比单参试验组模拟的固水含量更加集中。将各层云覆盖率与CALIPSO云产品的对比也发现,对于低层暖云降水过程,选择如WSM3单参云微物理方案比双参方案得到的模拟云量更加接近实况,而对于以深对流为主要运动特征的冷云降水过程,选择如WDM5或WDM6这样双参云微物理方案模拟得出的高云量值更加稳定,误差也更小。

In the present study,a heavy precipitation process of the Yangtze Valley River Basin during the period of 30 June to 4 July 2016 is simulated by using a Weather Forecast modeling system.The effects of the microphysics schemes are dividedinto two groups of nine single-moment and seven double-moment schemes.Next,using the time series of observational precipitation to simulate single-moment and double-moment schemes,FY-2G and Cloudsat cloud product were also used to evaluate the simulation different microphysics schemes of the cloud macroscale and microscale characteristics,such as total cloud fraction and vertical struction of the cloud fraction and cloud water content in the precipitation process.The results revealedthe following:the simulation of different microphysics schemes can present the rain belt position and central rainfall intensity of the process,yet the simulation of the cloud macroscale and microscale characteristics are significantly different.With the exception of the Kessler scheme by the warm cloud scheme of single-moment scheme,in which,due to the insufficient description of the ice cloud process causing the simulation of total cloud fraction to be significantly higher,all of the other single-moment and double-parameter schemes can simulate the temporal and spatial evolution characteristics of the total cloud cover during the heavy precipitation process.From the vertical distribution characteristics of cloud coverage and cloud water content,the simulation stability of the group of single-moment schemes to the middle and low level warm clouds below 600 hPa are slightly better than the group of the double-moment schemes.In addition,the simulation results of the ice cloud between 200—500 hPa were reversed,and the group of double-moment schemes was more concentrated than the single-moment group.The comparison of the simulation cloud fraction of each layer with the Cloudsat cloud product showed that for the low level warm cloud precipitation process using the WSM3 scheme of single-moment scheme the cloud fraction is closer to the observation than the double-moment schemes.However,the deep convection process which took the cold cloud precipitation process as the main movement characteristics,when using the WDM5 or WDM6 scheme of double-moment schemes,the high cloud fraction is more stable and the error is smaller.