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气象:2015,41(5):544-553
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北京7·21暴雨暖区中尺度对流系统的数值模拟
(中国气象科学研究院灾害天气国家重点实验室,北京 100081)
Numerical Simulation of Mesoscale Convective System in the Warm Sector of Beijing “7.21” Severe Rainstorm
(State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081)
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投稿时间:2014-09-05    修订日期:2015-04-14
中文摘要: 许多业务模式对北京2012年7月21日特大暴雨的预报均是以锋面降水为主。在冷锋过境前,实际北京西南部强降水主要以暖区降水为主。本文利用30个成员的中尺度非静力数值模式(WRF),通过3次集合卡尔曼滤波(EnKF)同化地面和探空资料,对这次暴雨过程进行了集合数值模拟。通过对比分析模拟降水较好与较差成员发现,好的成员能够模拟出河北中西部及北京西南地区触发出的暖区中尺度对流系统(MCS)以及相对稳定的系统配置,使得MCS在北京上空充分发展,从而较好地模拟了这次特大暴雨过程中的暖区降水;而较差的成员则没能模拟出暖区降水过程,降水以锋面降水过程为主,并且雨带位置偏南、出现时间滞后。集合成员间模拟结果出现的较大差异,和初始场中低值系统位置的较大差异有直接关系,因此通过EnKF提高模式成员初始场的准确率,从而准确模拟后期主要影响系统的移动和发展,是成功模拟暖区对流系统触发和维持的关键所在。
Abstract:A few operational models predicted the Beijing “7.21” (21 July 2012) severe rainstorm with the wrong reason that the severe convective rainstorm resulted mainly from cold front. In fact, a large amount of rainfall occurred over the warm area of the southwest of Beijing before the cold front. In this paper, after assimilating the surface and sounding conventional data three times by ensemble Kalman filter (EnKF) method, a non hydrostatic mesoscale numerical model (WRF) that has a collection of 30 members was employed to simulate the process. The comparison of a better member and a worse member reveals that the better member can successfully simulate the mesoscale convective system (MCS) in the warm sector in the central and western part of Hebei Province and the southwest of Beijing and the relatively stable system configuration, thus making the MCS fully develop over Beijing. So, it does a better simulation of the warm sector precipitation during the process of the severe rainstorm. In contrast, the worse member fails to simulate the precipitation in warm sector, and turns out to be frontal precipitation with the rain band southerly and the occurrence time lagged. The difference in these simulated results is greatly related to the corresponding simulated location of the low vortex in each ensemble member. The improvement in initial field of ensemble member by EnKF, which makes the simulated movement and development of main influence systems more accurate, is therefore the key to simulate the trigger and maintenance of the convective system in warm sector successfully.
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基金项目:国家重点基础研究发展计划(973计划)(2012CB417200)、国家自然科学基金项目(41075605)和中国气象局气象关键技术集成与应用项目(CMAGJ2013ZX ZH1)共同资助
引用文本:
王淑莉,康红文,谷湘潜,倪允琪,2015.北京7·21暴雨暖区中尺度对流系统的数值模拟[J].气象,41(5):544-553.
WANG Shuli,KANG Hongwen,GU Xiangqian,NI Yunqi,2015.Numerical Simulation of Mesoscale Convective System in the Warm Sector of Beijing “7.21” Severe Rainstorm[J].Meteor Mon,41(5):544-553.