“05.6”东北暴雨中尺度对流系统研究Ⅱ:MCS动力结构特征的雷达卫星资料分析

THE RAINSTORM AND MESOSCALE CONVECTIVE SYSTEMS OVER NORTHEAST CHINA IN JUNE 2005 Ⅱ:A SYNTHETIC ANALYSIS OF MCS's DYNAMICAL STRUCTURE BY RADAR AND SATELLITE OBSERVATIONS

应用多普勒雷达和卫星资料对2005年6月10日发生在黑龙江省沙兰河上游的暴雨MCS动力结构的演变特征作了进一步研究,以加深对东北暴雨中尺度对流系统动力学结构的认识。研究结果表明,导致2005年6月10日黑龙江省沙兰河上游暴雨的中尺度对流系统是一个具有多单体风暴结构特征的孤立对流系统,对流系统中个别对流单体的强烈发展导致了沙兰河上游的雷暴等剧烈天气过程。此外,研究还发现,对流系统在初生—发展—成熟3个阶段中,雷达反演的低空风场上显示出明显的规律性,随着降水加大,降水区附近的流场上反气旋性旋转疏散的特征显著增强。对整个对流系统来说,以对流云团移向方向(东北方)为前方,低空暖湿气流从云团左后方(西南方)入流,而在云团的右前方(偏东方)出流,即系统内的气流具有后方入流前方出流的特点。从对流系统的移动规律来看,云团左侧低空入流高空出流,右侧低空出流高空入流,即在云层平均风方向的左侧低空辐合高空辐散,右侧低空辐散高空辐合。这种有利于对流单体从系统的左后方新生,在右前方消亡的配置可能是导致沙兰河上游暴雨的雷暴云具有左移风暴特点的重要动力机制。

To further understand the dynamic mechanism of the MCS （Meso-scale Convective System） which was responsible for the rainstorm in the upper basin of Shalan River, Heilongjiang province on 10 June 2005, on the basis of the analysis in part I this part focuses on the dynamical structure and evolution of the MCS by using Doppler radar and satdlite observations. The analysis results indicate that （1） the mesoscle convective system resulting in the rainsotrm was an isolated MCS with a multi-cell structure; （2） some rapid growing convection individuals embedded in the MCS seems played as direct triggers to the severe local storm at the upper basin of Shalan River. Furthermore, the retrieval wind fields reveal that the low-level ambient wind fields of the MCS displayed evident regularity during the system＇s nascent, development and mature stages. With increase in the rainfall intensity, the anti-cyclonic and divergent winds at the lower troposphere within the precipitation area were intensified prominently. Relative to the whole convective system, the low levd warm and moist air flowed into the convective cloud duster from the left rear （southwest direction）, while downdrafts flowed out from the right front （northeast direction）. The system is characterized of a rear inflow and front outflow structure. Viewed from the moving direction of the MCS, on the left side, the inflow/outflow was at the lower/upper levd, while on the left side the inflow/outflow was at the upper/lower level, respectivdy. This configuration of upper and lower level air flows is favorable for convective cells spawning at the left rear and decaying at the right front of the MCS, which might act as a key dynamic mechanism for the left-moving rainstorm.