南疆西部两次极端暴雨中尺度特征对比分析

Comparative Analysis on Mesoscale Characteristics of Two Extreme Rainstorms in the West of Southern Xinjiang

利用常规气象观测、地面区域气象站逐小时观测数据、FY-2G云顶亮温、喀什CR/CC雷达产品及NCEP再分析等资料,对比分析南疆西部2020年4月17—24日和2021年6月15—17日(分别简称“过程1”、“过程2”)两次极端暴雨过程环流背景和短时强降水环境条件、中尺度特征。结果表明:两次过程均发生在500 hPa“东西夹攻”的有利环流背景下,100 hPa南亚高压分别呈东部型和双体型,低空急流、切变线和地面中尺度辐合线是两次暴雨重要的触发系统。两次强降水均发生在对流云团发展最强盛、范围最大时或TBB梯度最大处。但雷达回波特征明显不同,“过程1”影响系统为线性多单体强风暴,最大反射率因子达65 dBZ,具有中小尺度辐合和旋转特性,强降水期间VIL维持40 kg/m2以上并有跃增现象,更有利于产生强对流。“过程2”影响系统为分散性普通单体风暴,径向速度高层辐散不明显,VIL值明显小于“过程1”。

Based on conventional meteorological observations,hourly observation data from meteorological stations in the ground region,FY-2G cloud top brightness temperature,CR/CC radar products in Kashgar and NCEP reanalysis data,The circulation background,and mesoscale characteristics of two extreme rainstorm processes from April 17 to 24,2020 and June 15 to 17,2021(Process 1 and Process 2,respectively)in western Southern Xinjiang were compared and analyzed.The results show that both processes took place under the favorable circulation background of“east-west attack”at 500 hPa,and the 100 hPa SAH was east type and double type,respectively.Low-level jet,shear line,and surface mesoscale convergence line were the critical triggering systems of the two heavy rainstorms.The two heavy rainfall events occurred when the convective cloud cluster was the most powerful and its range was the largest or the TBB gradient was the largest.However,the radar echo characteristics are obviously different.The influence system of“Process 1”is a linear multi-cell strong storm with a maximum reflectivity factor of 65 dBZ,which has the characteristics of convergence and rotation at small and medium scales.During the heavy rainfall,VIL maintains over 40 kg/m2 and has a jump phenomenon,which is more conducive to the generation of severe convection.The system affected by“Process 2”was a dispersed typical mono storm,with no apparent divergence in the upper level of radial velocity.The Value of VIL was significantly smaller than that of“Process 1”.