Research on Atmospheric Conditions supporting MCSs over East China in Summer

East China is one of the areas that frequently influenced by mesoscale convective systems (MCS). The occurrence of strong convective disastrous weather caused by MCS in summer is a serious threat to the people's lives and property. By using TBB (black body temperature) data of FY-2E satellite, statistical research of Meso-α Convective Systems (MαCS) and Meso-β Convective Systems (MβCS) occurred over East China in summer (from June to August) during the year of 2010 to 2014 was carried out. This analysis showed that MCSs of these two scales mainly occurred in Anhui, Jiangsu, Jiangxi and Zhejiang areas, moved from west to east, and were nocturnal. Secondly, the analysis of the formation cause showed the shear line and low-level jet at 850hPa, subtropical high and short-wave trough in middle latitude at 500hPa and upper-level jet at 200hPa were the main atmospheric factors before MCS formed. The water vapor supply in the middle and lower troposphere, atmospheric instability in the low layer and the dynamic structure of convergence at low level and divergence at upper level were the necessary conditions for the formation of MCS. The weather situation before initiation of MαCS could be divided into two categories: In the first group, the system was located on the west side of the low-level jet stream, south of the cyclonic circulation at 850hPa, controlled by the southwest airflow before the trough at 500hPa, and was affected by the anticyclonic circulation at 200hPa. The second one showed obvious westerly flow in the south of the shear line at 850hPa, westerly flow at 500hPa and the upper-level jet at 200hPa. Between the two types of circulation situations at 850hPa before the occurrence of MβCS, the westerly in the southern part of the shear line controlled for the first type, while the southwest flow in the southern part of the shear line and low-level jet in east of the formation position belonged to the second category. Before the MβCS occurred, the formation position was located on the east of the short-wave trough at 500hPa, and the westerly jet stream at 200hPa matched with the middle and lower level.