天山北坡一次暴雨天气成因初探

A preliminary analysis of formational causes of a heavy rain in north slope of Tianshan mountain

利用常规气象资料、探空资料、多普勒雷达资料等对2007年7月16～17日发生在天山北坡的一次大暴雨天气过程进行分析。结果表明:(1)南亚高压双体型造成高低纬度槽脊叠加引导冷空气进入新疆,天山两侧的风切变产生的气旋性辐合加上地形的影响使冷空气堆积,为降水过程提供了有利的大尺度天气背景;(2)地面正负变压区的南北波动使准静止锋移动缓慢,孟加拉湾水汽持续向北输送造成天山地区有大面积水汽辐合区,导致降水持续时间长;(3)k指数的增大、沙氏指数的减小、高低空强烈的风切变以及涡度平流的高低空配置加强了垂直上升运动的发展,使局地大气潜能和不稳定度增加,具备触发暴雨天气发生的条件;(4)冷锋云系范围较大,最大TBB≥58℃。并在移动发展过程中得到了孟加拉湾热带气旋水汽持续补充,并以天山中部为轴呈逆时针旋转,造成大范围的降水;(5)雷达资料表现为混合云降水回波特征,回波呈反气旋方式旋转,在山区一带形成辐合,高低层冷暖平流以及中低层的风切变,为降水的产生及维持提供了有利的动力条件。

the rainstorm synoptic process in northern slope of Tianshan mountain（TSM） in July 16~17,2007 was analyzed based on the routine meterological data,radiosonde observation,Doppler radar material and etc.The results showed that South Asia high pair-type distribution made trough-ridge overlying from high to low latitude,leading cold air into Xinjiang,the cyclonic convergence produced by wind shear on TSM sides caused to cold air accumulation with the influence of terrain,providing advantage large-scale weather background for rainfall;the north-south fluctuation of surface positive-negative allobar made quasi-stationary front moving slowly.The bay of Bengal water vapor continuous transportation brought about large-area vapor convergence zone on TSM,leading to precipitation lasted for a long time;the increase of K index,decrease of SI,high-low severe wind shear and vorticity advection distribution strengthened the development of vertical upward motion,increased local atmospheric potential energy and instability,having the trigger condition of rainstorm;cold front nephsystem range was wide and the maximum TBB≥58℃,rotate at a slow speed taking the center of Middle Tianshan as axis,causing wide range precipitation;hybrid cloud echo was displayed on radar,spin at anticyclonic pattern and form convergence on TSM,high-low layer cold-warm advection supplied effective dynamic conditions for continuance and reinforcement of precipitation,that have a certain guiding significance to the accurate forecast of rainstorm in the future.