南疆西部一次罕见暴雨过程的成因分析

Cause Analysis on Rare Rainstorm in West of Southern Xinjiang

利用常规观测资料、T639初始场资料、NECP 1°×1°再分析资料、FY-2静止卫星和天气雷达资料,分析了2010年9月16-20日南疆西部一次罕见的暴雨过程。结果表明,暴雨发生在南亚高压双体型(高压中心分别位于伊朗高原和青藏高原东部)及中亚低槽向南的切涡有利大尺度环流背景下,高、中及低空三支急流的有利配置为暴雨的产生提供了动力和水汽条件,中小尺度辐合与对流是暴雨发生的直接始作俑者。这次暴雨过程的水汽来源有3部分:较深厚的中亚低涡西南气流所携带的水汽,中低层哈密南部至南疆盆地偏东气流的水汽集聚与辐合和中高层中亚南部偏南风所携带的暖湿气流接力输送。其中,85%的水汽输送来自偏东和偏南气流。强对流发生在暖区一侧,暴雨落区位于TBB最大梯度区并与云迹风的高层辐散相对应。3个时段的强降水均由混合性降水回波造成。其中,有中小尺度回波发展,但移动路径和强回波中心的位置有所不同。

Using the convention observation, T639, NECP data, stationary satellite and weather radar data, a rare rainstorm in West of Southern Xinjiang from 16 to 20 September 2010 was analyzed and there were three heavy rainfall time periods from 08：00 to 17：00 on 17, from 02：00 to 17：00 on 18 and from 08：00 to 17：00 on 19. The results showed that the rare rainstorm occurred the background of favorable large-scale circulation is double body of south asia high（high pressure center located in Iran Plateau and the east of Tibetan Plateau） and central Asia trough to south cutting vortex low. Favorable configuration a- bout three jet streams where the higher southwest, south in middle and lower east to provides the power and water conditions for the rainstorm. The mesoscale convection is the direct effect of rainstorm. Water vapor source payments calculation analysis showed that there are three parts of water vapor sources at three rainstorm stage： One is thick central Asian vortex itself carry water vapor from southwest airflow, the second is by east of airflow water vapor concentration and convergence from hami south to Southern basin on middle-low level, the third is conveying the relay water vapor that warm-moist from south air flow in South Central Asia on middle-high level, 85% of water vapor transmission from the east and south airflow. Severe convection occurres on warm side, rainstorm fall area located the maximum gradient of TBB and corresponds to a higher divergence of cloud drift wind. Three times of rainstorm caused by the mixed precipitation echoes, among them are the development of mesoscale convection, but three times of echoes are differently what moving path and strong center.