一次陇东大暴雨的锋生过程及倾斜涡度发展  

Frontogenesis Process and Slantwise Vorticity Development of a Rainstorm Process in the Eastern Gansu

作　　者：王伏村 许东蓓[2] 姚延锋 修韶宇 郭萍萍 阙龙凯 韩树浦 

机构地区：[1]张掖市气象局,张掖734000 [2]兰州中心气象台,兰州730020 [3]天水市气象局,天水741000

出　　处：《高原气象》2016年第2期419-431,共13页Plateau Meteorology

基　　金：公益性行业(气象)科研专项(GYHY201306006);中国气象局关键技术集成与应用项目(CMAGJ2014M54);甘肃省气象局气象科研项目(GSMAMs2016-07)

摘　　要：利用探空、地面加密自动气象站、卫星云图、天气雷达和ECMWF(ERA-interim)0.25°×0.25°再分析资料,从大气环流、云图和雷达回波特征、锋生及倾斜涡度发展等方面对2013年6月20日发生在甘肃陇东地区的大暴雨天气进行了诊断分析。结果表明:高原东北侧低空切变线、副热带高压及冷空气相互作用下,干冷空气和暖湿空气在中低空交汇产生强锋生,使切变线上垂直涡度、辐合快速发展,触发不稳定能量释放产生强对流,导致大暴雨发生。暴雨出现在TBB<-52℃的强对流云带中,雨强随着冷空气的向南侵入和渗透,由北向南在陇东地区逐步增强,进入四川后开始减弱。雷达强回波区高度<5 km,在0℃层以下具有低质心、暖云高效降水回波的特征。降水回波为南北带状,自南向北移动,不断影响同一地区,具有明显的"列车效应"。锋生强度与切变线强度及暴雨强度的增强、维持和减弱变化基本一致。分析锋生函数表明,在暴雨增强阶段,散度项锋生和形变项锋生起主要作用,形变项锋生作用更显著,倾斜项锋生作用相对较小;在暴雨持续阶段,散度项锋生和形变项锋生作用旗鼓相当,倾斜项起锋消作用。通过全型垂直涡度方程建立垂直涡度变化与锋生的直接联系,从而诊断锋生对天气系统强度的作用。锋生使得湿等熵面倾斜,在锋区前侧产生显著的正垂直涡度变化,切变线得到快速发展。By using the data of sounding and surface intensive AWS,the satellite cloud images,the Doppler weather radar and the reanalysis data of ECMWF（ERA- interim） 0. 25° × 0. 25°,the frontogenesis process and slantwise vorticity development of a rainstorm occurred on 20 June 2013 in the eastern Gansu are analyzed.The results show that the strong frontogenesis is caused by interaction among the shear line in lower troposphere,subtropical high,and the cold air in the middle and lower troposphere in the northeastern side of the plateau. The frontogenetical forcing causes rapid development of vertical vorticity and convergence in the shear line,triggering the release of unstable energy to generate strong convection and rainstorm. The rainstorm occurs beneath strong convective cloud of TBB- 52 ℃. Rain intensity changes from weak to strong with the cold air southward invading and infiltrating in the eastern Gansu,however,that begins to weaken after entering the Sichuan. The height of radar strong echo is below 5 km and 0 ℃ layer,it has characteristics of low center of mass and high efficiency precipitation echo. The strong echo moving from south to north has the train effect. The intensity changes of frontogenesis,shear line and rainfall are consistent. The frontogenesis function analysis indicated that enhancement stage in the rainstorm,effects of divergence and deformation play the main role and effect of deformation is more obvious,however,effect of tilting term is relatively small. The continuous stage in the rainstorm,effects of divergence and deformation are equal in match or contest of strength,effect of tilting term is frontolysis. Through the complete form of vertical vorticity tendency equation established the direct connection between the vertical vorticity change and frontogenesis,to diagnose the frontogenesis effect on the intensity of the weather system. The frontogenesis tilts the wet isentropic surface and produces significant positive vertical vorticity change in front of the frontal zone,which res

关 键 词：暴雨 低涡 切变线 垂直涡度 锋生 倾斜涡度发展 

分 类 号：P458.121.1[天文地球—大气科学及气象学]