摘要
综合利用T213再分析资料和高时空分辨率观测资料包括地面区域逐时加密观测资料,对2007年8月8—9日陕西关中特大暴雨过程的环境条件和中尺度系统进行了分析。天气学分析表明:500 h Pa西太平洋副热带高压和青藏高原高压形成的高压坝在陕西中部断裂形成东北—西南向切变线、250 h Pa西风急流入口区右侧发散场和700 h Pa东西向切变线相互配合是特大暴雨形成的有利环境条件;低层风向快速变化使关中暴雨区低空水汽经历了减小—突然增加—快速减小的过程,关中周围水汽通过偏东气流输送至暴雨区为暴雨的发生提供了水汽和位势不稳定条件,而水汽的快速变化又形成关中暴雨的突发性和历时短而强的特征;高空反气旋涡度的发展形成强烈的"抽吸作用"、双圈垂直次级环流和强垂直上升运动及其两侧的弱下沉运动形成的不对称结构是暴雨形成的动力机制。强降水的中尺度特征分析显示:强暴雨是由一个中α尺度对流系统(MαCS)的发生发展产生的,MαCS又是由2个中β尺度对流系统(MβCS)合并发展而成,其内部对流单体的发展合并和独立加强形成岐山、礼泉和高陵3个大暴雨中心,这些对流单体的发展是由地面中尺度辐合系统产生的,强降水的强弱与地面中尺度辐合系统的强弱有很好的对应关系,地面中尺度辐合系统的形成和加强可能是强降水的触发机制和增幅原因之一。
The process of a brief heavy rainfall on 8—9 August 2007 over the Central Shaanxi Plain was analyzed using the T213 data and high space and time resolution data including automatic meteorological observing station data. The results indicate that the brief heavy rainfall occurred under favorable largescale ciuculation backgrounds,including the break of high-pressured dam,which resulted from the development merge of Qingqhai-Tibet Plain pressure and the west Pacific Ocean subtropical high in the middle level at 500 h Pa,right flank divergence field of westerly jet entrance region in the upper level at 250 h Pa and the shear line's development in the low level at 700 h Pa. The amount of water vapor in storm experienced changes of decrease,sudden increase and fast decrease,which owed to wind direction fast changesat the low level. The vapor accumulation from surrounding areas of the Center Shaanxi Plain,which was achieved through the easterly current,had provided sufficient vapor and potential instability for the occurrence of the heavy rainstorm. The vapor increased so fast that the rainstorm occurred suddenly,and the rapid decrease of vapor made the rainfall last shortly. The dynamic mechanism of rainstorm was the formation of intense 'pavement pumping 'effect,the secondary circulation circle and the asymmetric structure between the strong vertical upward movement and the weak dowdward movement due to the development of the upper anticyclone vorticity. The automatic meteorological observing satation data and satellite image data showed that the heavy rainfall was caused by the occurrence and development of MαC S,which camefrom the mergence and development of M βC S. The convective cells merged,developed and enhanced individually to fo rm the different precipitatio ncenters at Q ishan,L iquan and Gaoling. The development of the convectiv ecells resulted from the surfacemesoscaleco nvergence system. The changes of strength of the precipitation had a good co rresponding rela-tionship with that of the surface mesoscale convergence system. The formation and development of the ground mesoscale convergence systems maybe the trigger and development mechanism for the heavy rain fall.
出处
《大气科学学报》
CSCD
北大核心
2014年第5期591-604,共14页
Transactions of Atmospheric Sciences
基金
国家自然科学基金资助项目(41175048)
中国气象局公共气象服务中心业务基金(K2014002)
关键词
特大暴雨
环境条件
中纬度高压坝
中启尺度对流系统
heavy rainfall
condition of circumstance
high-pressure dam in the middle latitude region
meso-β-scale convective system
