“8.13”黄淮北部暴雨云团的组织结构和触发机制

Organizational Structure and Trigger Mechanism of Rainstorm Cloud Clusters over North Huanghuai Region on 13 August 2010

利用FY-2E卫星资料、多普勒雷达监测及4Dvar反演资料、区域自动站和常规观测资料、NCEP分析资料,对2010年8月13日黄淮北部暴雨云团的组织结构、发展演变及形成机制进行研究。结果表明:暴雨云团形成发展于低涡切变形势下,低涡切变线、西南急流及边界层扩散南下弱冷空气是主要影响系统;高的对流不稳定能量、强的低层垂直风切变和持续发展的水汽条件是主要环境特征。不同区域云团的形成机制有差别,发展北上的西南急流促使MβCS旺盛发展。随着低涡发展,MβCS发展合并形成圆形MαCS,强暖湿气流强迫、弱冷空气扩散及地面辐合线是圆形MαCS形成发展的重要机制。γ或β中尺度气旋及辐合线在对流初生阶段起动力触发作用,辐合加强及辐合区的向后延伸导致对流云团的自身发展和后向发展;成熟阶段对流单体后部的强出流促使对流单体分裂,气旋式环流外围西南和偏南气流合并造成对流单体合并。MαCS成熟和衰亡期雷达上出现的线状对流系统具有明显强降水特征。

In this paper,FY-2E satellite data,Doppler radar products and 4Dvar assimilation data,regional automatic station data,conventional meteorological data and NCEP reanalysis data are used to analyze the organizational structure,evolution and formation mechanism of rainstorm cloud clusters over the north Huanghuai Region on 13 August 2010.The results indicate that the cloud clusters developed under the synoptic situation of low-vortex and shear.The southwest jet,low-vortex shear line and cold air were the main weather systems.The clusters＇ ambient characteristics included high instable convective energy,strong low-level vertical wind shear and sufficient moisture.MβCSs,which induced heavy rainfall during the early period,had different forming mechanisms.With the development of low-vortex,several MβCSs merged into a round MαCS.The force of warm moisture airflow in low level and convergence line on surface were the main mechanism of the round MaCS.γ or β mesoscale cyclone and convergence line created the dynamic triggering effects.Enhancement and extension backward of convergence area led to the self and backward development of MCS.Strong outflow at the back of convective cell during the mature stage caused the cells to break,and convergence of southwest airflow and south airflow on the edge of the cyclone circulation made the combination of convective cells.The linear convective systems that developed during the mature and decline phase of MαCS showed obvious characteristics of heavy rainfall.