Abstract:

In this paper, precipitation data from 3698 automatic stations in Beijing-Tianjin-Hebei region, Beijing radar echo data and air quality data in Beijing from Ministry of Environmental Protection were used. A heavy rainstorm occurring in Beijing in July 2016 was simulated by using the WRF model. Four cloud microphysical schemes (NSSL, WDM6, Thompson, and Morrison) were used to test the sensitivity of precipitation to number concentration of cloud condensation nuclei or cloud droplet. According to the observation in North China, three tests indicating clean, light polluted and heavy polluted background were conducted seperately in every microphysical scheme. The results show that with the increase of number concentration of cloud condensation nuclei or cloud droplet, the development of the convective system decreased in NSSL scheme. The average accumulated precipitation and hourly precipitation in Beijing area reduced in all four microphysical schemes, and in NSSL and Thompson schemes it was more evident. The area where the accumulated precipitation was greater than 250 mm in southwest part of Beijing decreased in NSSL and Thompson schemes. The mixing ratio of cloud water increased and that of rainwater decreased in all four microphysical schemes. In this rainstorm, NSSL and Thompson schemes were more sensitive to the number concentration of cloud concentration nuclei or cloud droplet, but for WDM6 scheme it was not sensitive.

Key words: cloud microphysical scheme, cloud condensation nuclei, precipitation, hydrometeors

摘要：

采用京津冀地区3698个自动气象站降水量资料、北京站雷达回波资料及环保部提供的北京地区空气质量数据，利用WRF模式模拟2016年7月发生在北京的一次暴雨过程，对比NSSL、WDM6、Thompson和Morrison 4种微物理方案中降水对云凝结核或云滴数浓度的敏感性。根据华北地区云凝结核的观测结果，在每个微物理方案中设计了清洁、轻度污染、重污染背景下的3组试验。结果表明：随着云凝结核或云滴数浓度的增加，NSSL方案中系统发展减弱最为明显。4种微物理方案均出现区域平均累计降水量和小时降水量减少的情形，且NSSL和Thompson方案更明显，NSSL和Thompson方案中累计降水量超过250 mm以上的区域面积在北京西南部地区逐渐减小。NSSL、Thompson及Morrison微物理方案中云水混合比不断增加，雨水混合比减少。对于此次暴雨过程，NSSL和Thompson方案对云凝结核或云滴数浓度比较敏感，而WDM6方案最不敏感。

关键词: 微物理方案, 云凝结核, 降水, 水凝物