一次梅雨锋暴雨过程多尺度特征的诊断分析  

A DIAGNOSTIC STUDY TO THE MULTI-SCALE CHARACTERISTICS OF A MEIYU FRONT HEAVY RAIN-FALL PROCESS IN 1998

作　　者：蒋建莹[1] 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：《测绘科技动态》2003年第6期673-683,共11页

基　　金：国家重点基础研究发展规划项目"我国重大天气灾害形成机理和预测理论研究"(G19980 40 90 6-12 )

摘　　要：文中对 1998年 6月 12～ 15日长江中下游地区入汛后最强的一次梅雨锋大暴雨过程进行了诊断分析。结果表明 ,此次暴雨是在 3种不同尺度天气系统的共同作用下形成的。中高纬的双阻型和副热带高压位置偏南 ,是引发该暴雨过程的大尺度背景条件 ;天气尺度的低压槽为该阶段的连续大暴雨提供了动力条件 ,它的前部存在一个低层辐合、正涡度和高层辐散、负涡度的带状区域。α中尺度上 ,该暴雨系统的垂直结构为中低层强烈的辐合和上层的辐散 ,其中心有着强烈的上升气流 ;同时在中高层 ,系统的南侧有一个高空急流强迫产生的次级环流。这种α中尺度暴雨系统的三维结构为强暴雨的形成提供了必要的动力、水汽和不稳定性条件。In this paper a typical Meiyu front process with heavy rainfall, from June 12th to June 15th in 1998 has been analyzed, which was the most intense event in the Yangtze River vareachesley in the rainy season. The results show that the Meiyu heavy rainstorm was brought out under a combination of three space-scale weather systems. The favorable large-scale background field is the Double-Block Highs pattern in Asia-Europe mainland at 500 hPa. Ural and Okhotsh (sea) were controlled by a blocking high, respectively. The Okhotsh (sea) blocking high blocked off the cold air from moving eastward easily, hence the cold air from polar was piled up in the west of Lake Baikal. At the same time, the Western Pacific subtropical High (WPSH) located anomalously southward at lower latitudes provided favorable environment for the warm and moist air moving northward. And the warm, moist air met with the cold air from the north in the middle and lower reaches of the Yangtze River. It is a favorable environment for the Meiyu pattern. While the synoptic scale trough provided dynamic conditions for the heavy rainfall. In the downstream of the trough, there existed a narrow belt, which had convergence, positive vorticity in the low-levels, coupled with divergence and negative vorticity in the upper-levels. It is a pronounced property of the Meiyu front. On meso-α-scale, the vertical structure was characterized by strong convergence in the low-levels and divergence in the upper-levels, which induced strongly ascending motion. At the same time, in the upper-levels, there existed a secondary-circulation forced by upper-level jet stream south to the system. Such a 3D structure on meso-α-scale provided necessary conditions for heavy rainfall, including dynamic conditions, moisture convergence and instability. Thus, a heavy rainfall was unavoidable.

关 键 词：长江中下游地区 梅雨锋 暴雨分析 中高纬双阻型 副热带高压 大尺度背景 多尺度特征 

分 类 号：P458.121.1[天文地球—大气科学及气象学]