天山北坡一次特大暴雨过程诊断分析

利用常规资料、NCEP1°×1°再分析资料对2007年7月16—17日天山北坡出现的特大暴雨过程进行了诊断分析。结果表明：暴雨发生在100hPa南亚高压呈双体型、500 hPa中亚低值系统在天山北坡东段稳定维持的环流背景下;沿天山两侧的强东西风切变组织了系统性的强上升运动、低层向山的偏北气流与天山北坡向北开口的喇叭口地形产生的辐合上升运动促使暴雨强度增大;暴雨区与低层辐合、高层辐散的气旋性涡柱区相对应;来自孟加拉湾沿高原东侧偏南气流北上的水汽,通过中高层的西南气流和低空的偏东气流两条路径接力输送到暴雨区;正位涡异常与暴雨的发生关系密切。

Analysis of a Major Rainstorm in the North Slope of Tianshan Mountains

On July 17, 2007, a major rainstorm occurred in the north slope of the Tianshan Mountains. The analysis results show that the circulation background of the rainstorm displays a two body pattern of South Asia high and stabilization of low system in the middle of Asia. On the condition of steady stratification, the systematic ascending motion in the both sides of the Tianshan Mountains, the northern airflow in low levels, and the orographic uplift all augment rainstorm precipitation. The rainstorm area is corresponding to the cyclonic vortex column, with the vapor transported to the rainstorm area from Bay of Bengal through high-level southwesterly winds and lower northeasterly winds. There is a close relation between positive potential vorticity anomaly and the rainstorm.