一次中-γ尺度短时大暴雨的成因及可预报性分析  

Analysis on the Causes and Predictability of a Meso-γ-scale Short-time Extreme Rainstorm

作　　者：肖贻青 娄盼星 刘菊菊 刘胜男 Xiao Yiqing;Lou Panxing;Liu Juju;Liu Shengnan(Shanxi Meteorological Observatory,Xi’an 710014,China;Key Laboratory of Eco-Environment and Meteorology,Qinling Mountains and Loess Plateau,Xi’an 710000,China;Shanxi Institute of Meteorological Sciences,Xi’an 710016,China)

机构地区：[1]陕西省气象台,西安710014 [2]秦岭和黄土高原生态环境重点实验室,西安710000 [3]陕西省气象科学研究所,西安710016

出　　处：《气象与环境科学》2022年第4期13-22,共10页Meteorological and Environmental Sciences

基　　金：陕西省自然科学基础研究计划(2022JM-142);灾害天气国家重点实验室开放课题(2022LASW-B20)。

摘　　要：利用常规气象资料、区域站加密数据、FY-4A卫星资料、ERA-5再分析数据、多普勒雷达数据及多模式预报数据,对2021年7月22日至23日在陕西东部山区发生的一次中-γ尺度短时大暴雨进行了分析。结果表明:此次过程受远距离台风外围偏东风水汽输送影响,对流层低层及边界层产生高温、高湿、高能,造成大气具有强的不稳定及较低的抬升凝结高度和自由对流高度,形成了有利于短时大暴雨的环境条件,地面辐合线是触发机制。由于对流层中下层水汽含量高,能量充足,沿着地面辐合线不断有生成的中-γ尺度对流云团发展。秦岭北麓的对流系统在地面中尺度辐合线附近生成发展,稳定少动,强降水时间较长;陕西省商洛市山阳县附近有大于45 dBZ的雷达回波,移动较慢并发展至5 km以上,与气旋性辐合中心及对流层中下层低空急流共同作用,加之列车效应,造成86.5 mm/h的极端短时强降水。本次降水过程表现出明显的地形效应,大暴雨发生在高海拔的秦岭北麓及山阳县附近的迎风坡处,高大山脉的阻挡使对流单体移动缓慢,而喇叭口状的迎风坡有利于加强上升运动,促进对流发展,造成降水量增加。该过程天气尺度动力条件弱,热力不稳定条件极为有利,全球模式和主观预报对此类短时暴雨的预报能力有限,多家模式漏报暴雨,主要原因是不能正确地预报触发机制;中尺度模式具有较好的参考意义,对短时暴雨的落区、范围和强度把握较好。A meso-γ-scale short-time extreme rainstorm that occurred in eastern mountains area of Shaanxi Province during 22-23 July,2021 is analyzed based on conventional observational data,FY-4A satellite data,ERA-5 reanalysis data,Doppler radar data and multiple models forecast data.The results show that the water vapor transport from the easterly wind outside the typhoon caused the high temperature,high humidity and high energy to be generated in the lower troposphere and boundary layer.As a result,the atmosphere had strong instability,low lifting condensation height and free convection height,forming favorable ambient conditions for short-time heavy rainstorm.The surface convergence was the trigger mechanism.Due to the abundant moisture and energy in lower troposphere,meso-γ-scale convective cloud clusters were constantly generated and developed along the ground convergence line.The convective system at the northern foot of the Qinling Mountains was restricted by the surface mesoscale convergence line,which made the convective cloud clusters stable and less moving and prolonged the time of heavy precipitation.This short-time extreme rainstorm of 86.5 mm/h was jointly caused by these elements:the radar echoes near Shanyang exceeding 45 dBZ which moved slowly and developed to more than 5 km,the lower troposphere easterly jet,the cyclonic convergence center and the train effect.Besides,topographic effect was shown obviously.This short-time extreme rainstorm occurred at the northern foot of the high-altitude Qinling Mountains and on the windward slopes of Shanyang.The convective clouds moved slowly due to the topographic obstruction of high mountains,while the bell-shaped windward slope enhanced the ascending motion,which resulted in the increase of precipitation.The dynamic conditions were weak in this process,but the thermal instability conditions were very favorable with abundant water vapor in the boundary layer.The prediction ability of global models and subjective forecasts for such short-time severe rainstorm was

关 键 词：短时暴雨 中-γ尺度 地形作用 列车效应 可预报分析 

分 类 号：P458.1+21.1[天文地球—大气科学及气象学]