北京一次强降水过程的数值模拟  

Numerical simulation on a heavy rainstorm process in Beijing

作　　者：蒋立辉[1] 张小宇[1] 庄子波[1] 

机构地区：[1]中国民航大学民航气象研究所,天津300300

出　　处：《气象与环境学报》2013年第4期18-25,共8页Journal of Meteorology and Environment

基　　金：国家重点基础研究发展计划(973计划)项目(2010CB731800);中央高校基金(ZXH2010D020)共同资助

摘　　要：利用新一代中尺度数值预报模式WRF 3.3和1°×1°的NCEP再分析资料,对2011年7月24日北京强降水天气过程进行数值模拟,并利用模式输出的高分辨率资料进行诊断分析。结果表明:WRF模式能较好地模拟出这次强降水过程。该过程不仅受到对流层中低层长波低槽和地面辐合区系统性的动力抬升作用,还受到对流层高层辐散的强迫作用。在这种配置下,中低层大尺度动力抬升与高层强辐散呈现出垂直耦合状态,有利于强降水区垂直环流和对流的发展。同时北京地区上空500 hPa以下相对湿度大于70%,在降水区形成了深厚的高湿环境,为降水的产生、加强和维持提供了充沛的水汽条件。从大气稳定度方面看,北京市全境均处于K指数高值区,高峰值为42.5℃,反映了大气层结非常不稳定。从动力作用分析发现,高空辐散、低空辐合的流场特征促进了降水的产生,螺旋度低层正值、高层负值的耦合结构是触发并维持降水的动力机制。Based on the NCEP reanalysis data with the spatial resolution of 1~ x 1 o grid, a heavy rainstorm process on July 24,2011 in Beijing was simulated by WRF 3.3（ Weather Research and Forecasting Model for version 3.3 ） model, and this process was diagnosed in terms of high resolution data from the model. The results indicate that this process can be well simulated using the WRF model. The heavy precipitation is affected not only by an uplift pow- er generated by the interaction of long-wave trough and the surface convergence in the middle and low level of troposphere, but also by the force of the divergence at the upper level of troposphere. Under these configurations, the large-scale dynamic uplift in the middle and low levels and strong divergence at the upper level are in a state of vertical coupling, which is favorable to the development of the vertical circulation and convection over the heavy rainfall region. At the same time,the value of relative humidity is greater than 70% below the 500 hPa over Beijing which forms a deep and humid environment for the generation of heavy rain,and provides abundant water vapor for generating,strengthening, and maintaining precipitation. On the basis of atmospheric stability, the K index is high in Beijing,and the peak value is 42. 5 ~C. It means that atmospheric stratification is unstable. The analysis of dynamical variables show that the flow field features of upper divergence and lower convergence accelerate the generation of precipitation. The coupling of negative helicity in upper level and positive value in lower level is the dynamical mechanism to trigger and maintain precipitation.

关 键 词：WRF模式 诊断分析 螺旋度 

分 类 号：P435[天文地球—大气科学及气象学]