摘要
利用客观分析资料和加强观测期资料,对1999年6月发生在我国长江流域的持续性梅雨期降水过程的大尺度环流特征进行了分析,结果表明:(1)1999年梅雨期,我国长江中下游强降水带状分布非常明显,强降水主要发生在长江中下游地区,强降水带呈东西向分布,并且雨带的南北边界非常清楚。(2)在对流层低层,从孟加拉湾来的西风气流和西太平洋副热带高压前缘的东南气流在长江流域维持,为此次强暴雨过程产生和发展提供了有利的大尺度条件。高空急流和低空急流的存在和维持为此次梅雨锋暴雨过程的发生提供了有利的抬升机制,而对流层中低层的中性对流不稳定特征则为持续性暴雨过程的发生提供了有利的不稳定机制。(3)梅雨锋区对流层低层的水汽辐合非常明显,水汽输送主要来自孟加拉湾和西太平洋,同时南海季风槽在向梅雨锋区输送水汽的过程中起到了非常重要的作用,它是热带海洋地区向我国内陆输送水汽的通道。(4)平均纬向风速u对流层高层出现了与高空西风急流与高空东风急流相对应的两个强风速核;径向平均风速v在400 hPa以下层次盛行南风,而在400 hPa以上的高层盛行北风;受两侧下沉气流的制约,梅雨锋降水带南北两侧存在位势不稳定层结中的不稳定能量无法释放,因此没有出现明显的降水。
Using the objective analysis and intensive observation period data,the large-scale features of Meiyu front associated with intense rainfall in low-and middle-reaches of the ChangJiang River in June 1999 are studied.The results are as follows：（1）The total precipitation has a west-east distribution and is concentrated within a narrow rainband,the southern and northern boundary of rainband is clear during Meiyu period of 1999.（2）The maintaining of westerly flow which come form the Bay of Bengal and southwest flow which around along the northwestern periphery of the western Pacific subtropical high provide favorable large-scale condition for the Meiyu front rainstorm.The presence and maintaining of upper-and lower jet provide favorable lifting mechanism,at the same time the character of neutral convective instability stratification provide favorable instability mechanism in the low and middle levels.（3）The convergence of moisture is obvious in the low level of troposphere over the area of Meiyu front.The transportation of moisture mainly come from the Bay of Bengal and the western Pacific ocean,and then monsoon trough in South China Sea is a moisture transport channel from tropic sea to China mainland and has important effect in moisture transportation to Meiyu front zone.（4）Two cores appeared in high levels of troposphere which corresponding to the upper westerly-and easterly-jet in the cross-section of spatial averaged zonal wind u;the cross-section of spatial averaged meridional wind v dominates the southerly under 400 hPa and the northerly above 400 hPa;the potential instability stratification locates on northern and southern sides of Meiyu front zone,which are restricted by the downdraft and the instability energy could not be released,and then in these areas have not intense rainfall.
出处
《高原气象》
CSCD
北大核心
2007年第3期563-571,共9页
Plateau Meteorology
基金
国家重点基础研究项目(G1998040907)资助
关键词
梅雨锋
暴雨
环流特征
Meiyu front
Rainstorm
Circulation characteristic
