摘要
通过对2002年6月8～9日陕南大暴雨过程进行数值模拟, 模拟结果较好地复制了这次陕南大暴雨过程以及与之相联系的影响陕南地区中尺度对流系统的发生、发展过程.位涡分析结果表明, 低层正值位涡扰动的存在是暴雨发生发展的重要条件.冷空气是从中层侵入西北地区东部, 这样就形成了较强的对流不稳定层结, 有利于对流降水的发生. 大巴山使秦岭山脊、汉江河谷降水减小, 使秦岭东南坡和渭河河谷下游降水增加; 而秦岭使汉江河谷、秦岭南坡降水增加, 使秦岭山脉本身和陕北地区降水减少, 秦岭山脉对降水的影响主要是通过地形产生的垂直次级环流实现的.
The weather systems and a related mesoscale convective complex, causing severe heavy rain in the southern Shaanxi Province during 8 - 9 June 2002, are successfully simulated with MM5 model. The analysis of meso-β scale synoptic systems indicates that the occurrence and development of the local and paroxysmal meso-β scale synoptic systems lead to this rain besides the helpful macro-scale conditions. The evolution of the meso-β systems depends mainly on the topography and the macro-scale conditions, among which the topography and convective instability are thought to be the most important. Results show that positive perturbation of potential vorticity in the lower layers is one of important factors for the formation and development of torrential rain, and the cold masses invade into the middle level of the eastern part of northwest district and result in strong instability which is favorable for convective rainfall. Furthermore, with the effect of terrain, the southern Shaanxi Province becames the center of this extremely heavy rain process. Precipitation increment caused by Daba Mountains occurs in the southeastern slope of Qinling Mountains and the lower reaches of Weihe River, while rainfall reduction by D-aha Mountains appears in the ridge of Qinling Mountains and Hanjiang River valley; Qinling Mountains makes precipitation increase in the area of Hanjiang River valley and the southern slope of Qinling Mountains, and decrease in itself and the northern part of Shaanxi Province, whose effect on rain is realized by secondary vertical circulation caused by topography mechanical and thermal forcing.
出处
《大气科学》
CSCD
北大核心
2005年第5期814-826,共13页
Chinese Journal of Atmospheric Sciences
基金
国家重点基础研究发展规划项目2004CB418300
关键词
暴雨
数值模拟
Β中尺度
位涡
地形
torrential rain, numerical simulation, meso-β system, potential vorticity, terrain
