秦岭大巴山地形对陕南强降水的影响研究

Study on Influence of the Mechanical Forcing of Mesoscale Topography on the Extremely Heavy Rainfall in Southern Shaanxi on 8～9 June 2002

通过对地形敏感性试验的数值分析,认为大巴山使秦岭山脊、汉江河谷降水减小;使秦岭东南坡和渭河河谷下游强降水增加,大巴山本身降水增加幅度最大;大巴山峡口地形将大量暖湿气流向北输送,在秦岭南侧和东侧的迎风坡上产生强降水,而峡口两侧由于地形阻挡气流通过,使其下游地区降水减少。秦岭使大巴山和汉江河谷、陕北降水增加,使山脉本身降水减少,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;秦岭的地形高度变化与山脊降水量具有反相关关系,与山谷降水量关系不明显。

By analyzing the results of the sensitivity experiments about topography causing extremely heavy rainfall in the southern Shaanxi Province during 8-9 June 2002, it is found that the precipitation increment caused by Daba mountains occurs in the southeastern slop of Qinling mountains and lower reaches of Weihe river, while rainfall reduction by Daba mountains appears in the ridge of Qinling mountains and Hanjiang valley; that the gap between Daba mountains play＇s an important role in transportation of humid warm air flows causing strong precipitation in the south- and east-slopes of Qinling mountains, that Qinling mountains make precipitation increase in the area of Daba mountains, Hanjiang valley and part of northern Shaanxi Province, and decrease in itself, whose effect on rainfall is realized by secondary vertical circulation caused by topography mechanical and thermal forcing, and that elevation change of Qinling mountains have a reverse correlation with precipitation on the mountains and no remarkable relation with precipitation in Hanjiang vellay.