Mesoscale Characteristic and Trigger Mechanism of Rainstorm Cloud Clusters over North Huanghuai Region in China

In this paper, FY2E satellite data, Doppler radar products and 4DVAR assimilation data, regional automatic station data, conventional meteorological data and NCEP reanalyzed data were used to analyze the organizational structure, evolution and formation mechanism of rainstorm cloud clusters in north Huanghuai region on August 13, 2010. The results indicate that the cloud clusters develop in the synoptic situation of low-vortex and shear, and southwest jet, low-vortex shear line, cold air are main weather systems. The clusters’ environment characteristics include high instable convective energy, strong low-level vertical wind shear and sufficient moisture. MβCSs，induce heavy rainfall during the early period, have different forming mechanism. With the development of low-vortex, several MβCSs merge into a round MαCS. The force of warm moisture airflow in low level and convergence line on surface are main mechanism of the round MαCS. γ or β mesoscale cyclone and convergence line play the role of dynamic triggering effects. Enhancement and extension backward of convergence area lead to self and backward development of MCS. Strong outflow at the back of convective cell during the mature stage can promotes to divide the cell, and convergence of southwest airflow and south airflow on the edge of the cyclone circulation makes the combination of convective cells. The linear convective systems developing during the mature and decline phase of MαCS show obvious characteristics of heavy rainfall.