摘要
本文对1986年6月22日出现于长江中游的一次中低压过程进行了诊断分析。这个中低压水平尺度约500km，生命史为一天，但是形成了日降水量263mm的特大暴雨。分析揭示，梅雨锋是一条近于东西走向的正涡度带状分布区。而这一带状区中存在强烈的中尺度水汽通量辐合中心和深厚的上升运动区，有利于中尺度低压的形成。M和θ的剖面表明，条件对称不稳定（CSI）可能是这次梅雨锋暴雨的一种触发机制。此外，由拉格朗目方法对气块三维轨迹的计算表明，来自高低空和不同方向的两支大尺度气流的结合使高空辐散加强，可能对中低压的发展有帮助。
It is found that mesoscale lows occur often on Meiyu (Baiu) front in Summer. There is close rela-tionship between the low system and heavy rainfall. A typical case from 21 to 22 jUNE 1986 has beenanalyzed. The conclusions are as follows: (1) Meiyu front is located in a banded zone of positivevorticity. The mesoscale low develops near the maxima of convergence of moisture flux. (2) The verticalcross sections of M and show that conditional symmetrical stabi1ity is a possible triggering mecha-nism for the occurrence of heavy rainfall on the Meiyu front. (3) Three dimensional trajectory analysisof air parcels show clearly that confluence of the two different nows coming from upper and lowerlevels, respectively, was very significant and result in very strong divergence in upper levels. Themesoscale low systems formed in this favourable environment of middle reaches of the Yangtze River.
出处
《大气科学》
CSCD
北大核心
1994年第4期476-484,共9页
Chinese Journal of Atmospheric Sciences
基金
国家自然科学基金!49275240
