一次特大暴雨过程的多普勒天气雷达资料分析

Analysis on Doppler weather radar data of an extraordinarily heavy rainfall

利用卫星云图和多普勒天气雷达资料对2008年8月1—2日上午发生在安徽东南部及江苏西南部特大暴雨过程进行了分析。结果表明,这次区域性特大暴雨是由台风减弱演变为深厚低压系统所引发,暴雨区域辐合上升运动强烈,西南低空急流强盛,同时中层冷空气侵入触发不稳定能量释放;特大暴雨的发生与中β尺度强对流云团多次发展以及长时间维持密切相关,中尺度云团的最冷云区亮温和面积决定了暴雨强度;积层混合云降水回波内部有多个尺度不等的的对流回波相继经过暴雨发生地形成"列车效应",从而造成持续性暴雨,暴雨回波的强回波核总是位于云体的中下部,这是暴雨回波的典型特征;特大暴雨发生阶段,对流层中低层辐合厚度增加,强度增强,同时低层(2 km以下)伴随下沉运动,2 km以上则为上升运动。

Based on the satellite cloud picture and Doppler weather radar data,the extraordinarily heavy rainfall from 1 August to 2 August,2008 occurred in southeast of Anhui province and southwest of Jiangsu province was analyzed.The results show that the rainstorm was caused by re-intensified depression as the result of landfall of typhoon.There was severely convergent ascending motion and southwest low-level jet over rainstorm area.The cold air-mass which was intruded into middle troposphere triggered the instability energy.The severely heavy rainfall correlated with several times＇ developments and long standing maintenance of the meso-β scale MCS.Both the lowest cloud field luminance temperature and the area of meso scale cloud cluster decided the rainstorm intensity.And the area of the temperature below-73 ℃ of cold cloud cluster correlated with rainstorm area very well.Several convection cells inside the cumulus-stratus mixed echo passed through rainstorm area in turn and brought about ＂train effect＂ and led to a sustained rainstorm.During heavy rainfall stage,the thickness of convergence in middle and low troposphere increased and intensity reinforced.The divergence in upper troposphere was weak.Descending motion prevailed in low troposphere（below 2 km） and ascending motion was above 2 km.