不同云微物理方案对“7.21”特大暴雨模拟的对比试验

Simulation contrast of different cloud microphysical schemes on the torrential rainfall event in Beijing on 21 July,2012

利用中尺度数值模式WRF v3.5.1中的17种不同云微物理过程参数化方案,对2012年7月21—22日北京特大暴雨过程进行了对比试验。模拟结果表明:不同云微物理方案对不同量级降水的模拟效果各有优势。NSSL 1-momlfo方案对中雨和大暴雨两个等级降水的模拟效果最好,降水中心值最接近实况;Eta(Ferrier)和Kessler方案分别对大雨和暴雨等级降水的模拟效果最好。总体上,能够较好地模拟出本次特大暴雨过程的方案依次为:NSSL 1-mom、NSSL 1-momlfo和Milbrandt 2-mom方案,而WDM6方案的模拟效果最差。云中水成物演变特征表明,模拟较好的方案中液态水、云冰和霰的含量较多,且随时间演变与地面降水强度的变化相一致。另外,模拟较好的方案中冰相粒子多,过冷水的范围大、含量高,有利于各相态粒子相互转化,促进冰相过程发展,致使降水量增多。

17 cloud microphysics parameterization schemes of the weather research and forecasting modeling system（ WRF v3. 5. 1 version） are used to simulate the torrential rain event over Beijing on July 21-22,2012. Results show that is terms of the simulation effects on precipitation of different levels each microphysical parameterization scheme has its advantage. The NSSL 1-momlfo scheme well simulates the moderate and torrential rainfall,in particular,the location and intensity of the rainfall agree well with observations. The Eta（ Ferrier） and kessler schemes simulate the heavy rain best. Overall,the successful simulation schemes on this torrential rainfall are NSSL 1-mom,NSSL 1-momlfo and Milbrandt 2-mom schemes,while the WDM6 scheme performs worst. In addition,when the mentioned above＂good schemes＂are used,the simulated variations of cloud water,cloud liquid water,cloud ice and graupel are consistent with those of the observed precipitation. For these ＂good schemes＂,the WRF model alsosimulates much more ice particles and wider of range super-cooled water,which are able to promote the development of ice-phase process,finally leading to more precipitation.