Based on the data from the Doppler radar,two wind profilers in Baodi and Xiqing,the tower in Tianjin,as well as NCEP/NCAR 1°× 1° reanalysis data,radiosonde data,intensified automatic surface observation data and automatic station minute data,a thunderstorm case in Tianjin on 8 June 2014 is analyzed.The results show:(1) It is a thunderstorm gale case of the northwestern current type,in which the wind vertical shear with a large temperature lapse rate was favorable for the occurrence of disastrous gale.(2) This case experienced three stages:bow echo complex,gust front,and cell bow echo.The intensity of the thunderstorm wind was related to the falling time and the height of the echo core:the higher extension of height,the shorter the falling time,the stronger of the thunderstorm.(3) The rapid movement of a strong cold pool was direct cause of the bow echo complex.The wind profiler data indicate that the intrusion of dry cold air was at 2.3 km in the bow echo complex,with a 10 minute lead time for wind gust in the surface.The surface mesoscale convergence line matching with surface highly unstable region triggered the thunderstorm at the stage of the cell bow echo.(4) When the gust front approaching,the rising flow was in coexistence with the sinking flow;the sink flow began at the boundary layer below 1.5 km with the maximum up to 0.9 m· s-1 at 630 to 750 m.The downward propagation of the sinking velocity peak indicated the emergence of the gust about 20 minute in advance,while the upward was above 2 km in the middle and lower troposphere.%利用多普勒天气雷达、宝坻和西青两部风廓线雷达、天津250 m气象铁塔观测资料,结合NCEP再分析资料、探空资料、地面加密自动站和自动站分钟资料,对2014年6月8日发生在天津地区的一次弱降水雷暴大风过程进行分析.结果表明:①此次过程属于西北气流型雷暴大风,低层强垂直风切变和较大的温度直减率为雷暴大风的出现提供有利环境条件;②此过程共经历弓形回波复合体、阵风锋和单体弓形回波3个阶段,雷暴大风的强度与强回波核伸展高度以及下落时间有关,回波核伸展高度越高,下落时间越短,雷暴大风强度越强;③强冷池的快速移动是弓形回波复合体阶段雷暴大风的直接原因,冷空气首先从2.3 km高度入侵,10 min后地面出现雷暴大风.天津南部具有不稳定能量高值中心,配合地面中尺度辐合线的触发作用导致单体弓形回波阶段雷暴大风;④阵风锋阶段上升与下沉气流共存,下沉速度峰值的下传特征较地面雷暴大风的出现提前20 min,2 km以上的对流层中低层为上升运动.
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