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Precipitation mechanism and organization of mesoscale convective systems.

中尺度对流系统的降水机制和组织。

基本信息

批准号：
06452411
负责人：
KIMURA Ryuji
金额：
$ 3.58万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

项目摘要

A heavy rainfall associated with the Baiu front was observed during an intensive observation period in the Kyushu District in July 1988. We studied a structure and mechanism of a rainband caused the heavy rainfall. A retrival method was developed to raveal a thermodynamic field in the rainband. The retrived field showed that the evaporation of raindrop and a vertical shear were important to maintain the inteese rainband.A numerical prediction experiment of the heavy rainfall was performed. The observed rainfall was simulated well and the environmental condition of the rainfall was stduied. A numerical model with high horizontal resolution was used to find a detailed structure of the heavy rainfall. The rainband was simulated and its vertical structure was clarified.A narrow cloud band developed over Kanto Plain on 22 April 1992 in association with the passage of an extratropical cyclone. Its unique features include the rapid formation and appcarance of an arc-shaped solid cloud wall, rather than a line of a number of isokated convective cells. It evolved along the southern edge of a much broader weak rain area in a manner similar to the embedded areal type as identified by Bluestein and Jain (1985).A mesoscale analysis of conventional observation data reveals that a local cold air mass propagated southeastward from the northwestern part of Kanto Plain. It was driven by the horizontal pressure gradient force associated with the eastward-propagiting cyclone. The cloud band was found to be forced to form when and where the cold surge collided with the synopic scale southwesterly flow which was prevailing over the southern part of Kanto Plain.It is further revealed that the cold surge was a leading part of a low-level mesoscale air mass which was termed as "forerunner". It was so named since it existed in front of the sysnoptic scale northwesterly flow and beneath the southwesterly flow ahead of the upper-level trough.

1988年7月，在九州地区的密集观测期间，观测到了与巴乌锋面有关的暴雨。对这次暴雨过程的雨带结构和形成机制进行了研究。本文提出了一种反演雨带热力场的方法。反演结果表明，雨滴蒸发和垂直切变是维持中间雨带的重要因素。对观测到的降雨进行了较好的模拟，并对降雨的环境条件进行了研究。利用一个高水平分辨率的数值模式对这次暴雨进行了详细的结构分析。1992年4月22日，关东平原上空出现了一条狭窄的云带，这条云带是与一个温带气旋的通过有关的。它的独特之处是迅速形成和出现弧形固体云壁，而不是一排等方位的对流单体。它沿着一个更广阔的弱雨区的南部边缘发展，其发展方式类似于Bluestein和Jain（1985）确定的嵌入区域型。常规观测资料的中尺度分析表明，一个局地冷空气团从关东平原西北部向东南方向传播。它是由与向东传播的气旋有关的水平气压梯度力驱动的。结果表明，冷涌与关东平原南部盛行的天气尺度西南气流发生碰撞时，云带是被迫形成的，冷涌是低层中尺度气团的先导部分，被称为“先导”。由于它位于高空槽前的综合尺度西北气流的前方和西南气流的下方，故得名。