陕南一次区域性短时强降水过程成因分析

利用实况降水资料、MICAPS观测资料、风云卫星红外资料以及新一代多普勒天气雷达产品,从环流形势、影响系统、雷达回波等方面对2015年5月7日晚陕南中东部的一次区域性短时强降水过程成因进行了分析,探讨此次强降水过程的发生机制和预报指标分析。结果表明,此次强降水过程发生在东亚一槽一脊的天气背景下,700和850 h Pa切变线叠加、地面存在冷锋和辐合线、低空西南暖湿气流强盛,为强降水过程提供了充足的水汽;高空急流配合低层中尺度切变线形成高层辐散、低层辐合形势,为短时强降水过程提供了充足的能量和动力。过程中水汽饱和程度迅速增大,在强烈垂直运动作用下强迫抬升凝结产生强降水,其中水汽主要来自落区上空空气中本身。雷达回波显示,过程中强回波区逐渐形成带状回波,所经过区域出现雷暴大风等灾害天气;同时强降水回波带(≥55 d BZ)在向东南平移的过程中,其自身也有从西南向东北方向的传播移动,造成洋县、旬阳、平利等站出现短时强降水。

The Causes Analysis of a Regional Short-time Heavy Rainfall in Southern Shaanxi

Using live precipitation data,MICAPS observation data,satellite infrared data and new generation Doppler weather radar products,a regional short-time heavy rainfall process in southern Shaanxi on May 7th in 2015 was analyzed from aspects of circulation situation,impact sys-tem,radar echo,the occurrence mechanism and forecast index of the heavy rainfall process was discussed.The results showed that the heavy rain-fall process occurred in the weather background of east Asia "one trough and one ridge", and the joint of shear line between 700 hPa and 850 hPa,the ground had cold front and the convergence line,the low-level southwest strong warm air provided sufficient water vapor for the heavy rainfall process,meanwhile the upper level jet stream and low level mesoscale shear line formed the situation of upper level divergence and low level convergence,which provided sufficient energy and power for the short time heavy rainfall process.The saturation degree of water vapor in-creased rapidly in the process,and the heavy rainfall caused by forced uplifting and condensation under strong vertical motion,in which the water vapor mainly came from the air over the area.The radar echo showed strong echo region gradually formed the band echo,the area had thunder-storms,strong winds and other disasters where it gone through;meanwhile,it also had its own movement from the southwest to the northeast in the process of translation to the southeast of the strong precipitation echo band (≥55 dBZ) ,which resulted in short-time heavy rainfall in the stations of Yang County,Xunyang County,and Pingli County .