一次梅雨锋暴雨过程的β中尺度对流系统发展机理的数值研究  

NUMERICAL STUDY OF THE EVOLUTION MECHANISM OF MESO-β SCALE CONVECTIVE SYSTEM ALONG THE MEI-YU FRONT

作　　者：江晓燕 倪允琪[2] 

机构地区：[1]南京大学大气科学系,南京210093 [2]中国气象科学研究院,北京100081

出　　处：《气象学报》2005年第1期77-92,共16页Acta Meteorologica Sinica

基　　金：国家重点基础研究发展规划项目 (G19980 40 90 6 12 )。

摘　　要：20 0 2年 6月 18～ 19日在湖北省发生的一次中尺度降水过程主要是由一个中尺度对流云团的活动造成的 ,且该中尺度对流云团在不断东移的过程中分裂成两个 β中尺度对流云团。文中使用中尺度非静力模式MM5对该次暴雨过程进行了数值模拟 ,研究它的发生发展机制。模式很好地模拟了造成该次强暴雨的中尺度对流系统的整个发展过程 ,模拟的降水分布与实况比较接近。分析模拟结果发现 ,中尺度对流系统在不断东移的过程中 ,受高层的辐散性流场的抽吸作用和低层的对流不稳定而发展加强 ;受地形的作用而分裂成两个对流单体 ;最后由于中高层水汽凝结降落后造成的水汽不足 ,高层的辐散气流明显减弱变得无组织和下沉气流的影响对流系统开始衰亡。通过以上的分析给出了引起该次梅雨锋暴雨过程的中尺度对流系统的发展演变模型。On 18-19 June 2002, a mesoscale convective system developed in Hubei Province along the Mei yu front. The synoptic situation showed that the mesoscale convective system was influence by the shear line at 850 hPa. From the Tbb data, the evolution of the convective cloud clusters was very clear. It was obvious, during this event, the mesoscale convective system split into two meso β scale convective systems when it moved toward the northeast. To understand the evolution mechanism of the MCS, numerical simulations for this event was performed using mesoscale model (MM5). The model successfully captured the evolution of the MCS, including the vertical structure. Due to the divergence in the high level and the convergence in the low level, the MCS was strengthened. In addition, the divergence in the high level was the cause of the movement of the MCS. And influenced by the orography, when the MCS moved to the mountain, it separated into parts. From the sensitivity experiment of the mountain, the orography was shown to be important for the splitting of the MCS. The existence of the mountain not only contributed the low level convergence and enhanced upslope winds, but also made the MCS separated and to dissipate. The results indicated the mountain wave was produced when the air current passed by the orography. Then, because of the reduction of moist air in the mid-level and the downdraft of the mountain wave, the meso β scale convective systems were weakened. According to the analysis, a conceptual evolution model of the MCS along the Mei yu front has been achieved.

关 键 词：Β中尺度对流系统 暴雨过程 梅雨锋 数值研究 发展机理 中尺度对流云团 2002年6月 非静力模式 降水过程 数值模拟 发展机制 发展过程 模拟结果 降水分布 抽吸作用 水汽凝结 下沉气流 演变模型 湖北省 MM5 强暴雨 不稳定 

分 类 号：P458.121.1[天文地球—大气科学及气象学] P426.62