一次东风波大暴雨过程诊断分析  

Diagnosis of a Heavy Rainfall Event in 1988 Caused by Easterly Wave

作　　者：顾思南 陈从夷[2] 刘建勇 徐迪峰 

机构地区：[1]浙江省宁波市气象台,宁波315012 [2]成都信息工程学院大气科学学院,成都610225

出　　处：《气象科技》2013年第4期726-735,共10页Meteorological Science and Technology

基　　金：国家公益性行业专项(GYHY201006004);宁波市社会发展公益公关项目(2009C50031)资助

摘　　要：利用美国环境预报中心0.5°气候预报系统再分析资料,研究了1988年"7.30"浙东大暴雨过程,发现低空南、北两支东风扰动的合并及其与高空急流的相互作用是暴雨产生的主要原因。高空冷涡与华北高压共同强迫,形成了东南向的高空急流;急流具有明显的动量下传特征,加大了对流层中层的东风分量,构成深厚的东风波系统。"7.30"过程的对流有效位能主要是海上气团的平流输送。低压倒槽的切变辐合积聚了大气的水汽含量,形成深厚的高相当位温层。对流层高层存在冷平流,使得东风波西移过程中对流有效位能能够持续稳定。风暴相对螺旋度与东风波系统匹配较好,能够清楚反映南、北两支东风扰动的合并过程。风暴相对螺旋度移动速度略快于东风波系统和垂直涡度,能够提前预报东风波降水的落区。The heavy rainfall process occurred on 30 July 1988 around the southeastern coast of Zhejiang Province is investigated by 0.5° NCEP Climate Forecast System Reanalysis data. It is found that the heavy rainfall was mainly caused by the merging of two low-level east-wind perturbations from south and north, respectively, and its interaction with upper-level jets. The south and north branches of the easterly wave originated from the abrupt westerly, southerly evolution of the subtropical anticyclone, and the development of convective perturbations triggered by the typhoon inverted trough, respectively. The east- west oriented upper-level jet was formed under the combined forcing of the upper-level cold vortex and the Huabei anticyclone system. The upper-level jet possessed an obvious downward transmission feature in momentum, which would enhance the easterly wind component at middle troposphere and form a deep easterly wave system. The convective available potential energy （CAPE） in the heavy rainfall event of 30 July 1988 was mainly caused by the advection of air mass on the sea. The convergence in low pressure converted trough could accumulate water content in air and form a deep level with high equivalent potential temperature~ This high equivalent potential temperature level may moved westward along with the easterly wave system and concentrate CAPE to convection development. There existed cold advection at the upper troposphere which could make the value of CAPE maintain steady during the westerly moving of easterly wave. The potential possibility of heavy rainfall caused by moving easterly wave could not be predicted by the single point sounding on the ground. The storm relative helicity matched with the easterly wave system very well and from it the emerging process of the south and north branches of east-wind perturbations could be reflected clearly. The moving speed of the storm relative helicity was a little faster than that of the easterly wave system and vertical vorticity, and therefore the storm rel

关 键 词：东风波 暴雨 对流有效位能 风暴 相对螺旋度 

分 类 号：P458.121.1[天文地球—大气科学及气象学]