华南暖区强对流降水系统的结构和闪电特征分析

Characteristic Analysis of Structure and Lightning for Convective System Produced Heavy Precipitation in Warm Sector of South China

利用加密地面观测资料、多普勒雷达资料及广东省地闪资料,研究了24h内影响华南珠江三角洲的两次中尺度强降水系统的结构特征和地闪特征。结果表明:(1)第一次对流系统以后建型方式(back-building)组建,垂直结构类似海上对流,水平结构类似平行层状的对流系统。第二次对流系统垂直结构倾向于陆地的对流,水平结构类似于拖曳层状的对流系统。(2)地闪分布特征:两个系统在其生命史中负地闪占据主导地位;第一次对流系统在发展期正地闪逐渐增大,从成熟到衰减期正地闪逐渐减弱,第二次对流系统从发展到消亡期正地闪逐渐增大。第一次对流系统成熟期:在低层强回波移动方向右侧为正地闪,左侧为负地闪。对流系统地闪主要集中在对流区(92.8%的地闪),部分在对流区下风方(7.2%的地闪)。第二次对流系统特征:正、负地闪大部分重叠出现在对流区(78%的地闪),部分在尾随的层状降水区(22%的地闪)。正、负地闪在非对流区发生的概率比第一次系统的大。两个系统中88%以上的地闪集中在6km高度、回波>25dBZ以上的范围。

The fine density surface observation data,Doppler radar data,and cloud-to-ground（CG） lightning data in Guangdong region were utilized to study the characteristics of structure and CG lightning of two convective systems,which occurred within 24 hours over Zhujiang delta,South China.Results showed that：（1） the first convective system（occurred in morning） exhibits similarity to parallel stratiform MCS,the convective cells in the first system are organized by way of back-building,the vertical structure is similar to those of marine convective.While the second system exhibits similarity to trailing stratiform MCS,the vertical structure tend to those conventions over continent.（2） The characteristics of lightning are as follows：（I） The negative CG lightning predominate in the whole lifetime of convective systems for both the systems.（II） The percent of positive CG lightning gradually increases in its development stage,then decreases from mature to dissipation stages for the first convective system,while the percent of positive CG lightning gradually increases during the lifetime of the second convective system.（III） At the mature stage of the first convective system,the negative CG lightning occurs just behind of intense reflectivity at low level,positive presents its head.Lightning concentrates in intense reflectivity area（928% of lightning） and partly occur on the leeward side of intense reflectivity（72%）.As for the second convective system,the positive and negative CG lightnings mostly overlap in the intense reflectivity area（78%）,and partly occur in the stratiform area（22%）.The possibility of occurrence of lightning in stratiform region for the second convective system is larger than that of the first convective system.More than 88% of CG lightning occurred in a region with reflectivity value equal or greater than 25 dBZ at the height of 6 km at the mature stage for both the systems.The characteristics of structure of convective system and its lightning are also discussed.