受“碧利斯”影响的一次中尺度对流系统模拟研究

Numerical simulation on mesoscale convective systems associated with severe tropical storm "Bilis"

利用中尺度数值模式WRF(weather research and forecasting model)对2006年7月16—17日在我国华南沿海地区引发强降水的中尺度对流系统(mesoscale convective systems,MCS)活动进行了数值模拟,并结合观测资料对此次过程进行分析。结果表明,1)此次MCS活动与0604号强热带风暴"碧利斯"减弱而成的热带低气压及西南季风密切相关。热低压为MCS的发生提供了动力抬升条件,西南季风则承担了输送水汽的角色,二者的持续结合,使华南大部地区中尺度对流系统不断发生和发展,形成强降水。2)该MCS具有明显的不对称结构,云体越向上越向南部伸展,云系主要分布在热低压的南部,呈东北—西南走向的带状。3)模式对此次MCS强降水过程的模拟效果较好,客观地反映了此次MCS的发展演变及雨带的分布状况。4)在广西境内的中尺度对流云团中云水含量较少,冰相粒子的比含水量值很大,主要的降水机制为冰晶降水机制。

The Mesoscale Convective Systems（MCS） in the coastal areas of South China during 16th 17th July 2006 was simulated using mesoscale numerical model WRF（ weather research and forecasting model）, and we analyzed the precipitation process combining with observation data. The results show that ： 1 ） The activity of MCS was closely related to the remnant of the downgraded severe tropical storm ＂Bilis＂ and southwest monsoon. The tropical depression provided dynamic conditions for MCS and southwest monsoon brought plenty of aqueous vapor to South China, the continued combination of trop ical depression and southwest monsoon caused the formation and development of MCS;2） The MCS has an obvious asymmetry structure, the upper cloud stretched to south and the nephsystem distributed in a northeastsouthwest band and mainly located in the south of tropical depression;3 ） Using WRF model to simulate the heavy rain process produced good results, which represented the development of MCS and the distribution of rain band ;4） The cloud water content was little and ice crystal content was large in the mesoscale convictive cloud cluster, so ice crystal precipitation mechanism was the main pre cipitation mechanism.