A 10-Year Climatology of Mesoscale Convective Systems and Their Synoptic Circulations in the Southwest Mountain Area of China

摘要

Hourly blackbody temperature data from the warm seasons (May-September) of 2009-18 were used to detect mesoscale convective systems (MCSs) generated in the southwest mountain area (elevation >= 500 m) of China. A total of 3059 MCSs were grouped into four categories (C1, C2, C3, and C4) according to their generation positions using K-means clustering. Major characteristics of the four types of MCSs and their synoptic environmental conditions were investigated. The MCSs had a peak in July and a minimum in May, and usually lasted from 3 to 21 h. The C1 MCSs generated in the northeast of the Tibetan Plateau developed faster, were largest, and had a longer lifespan. The C2 and C4 MCSs had greater intensity and were initiated in the southeast of the Tibetan Plateau and the west of the Yungui Plateau, and near the Wuling and Xuefeng Mountains, respectively. The C3 MCSs initiated in the Qinling, Ta-pa, and Wushan Mountains were smallest. The C1 and C2 MCSs contributed more than 30% to total precipitation, which was more than the C3 and C4 MCSs (<25%), and the contribution rate of MCSs to short-duration heavy rainfall affected by local MCSs was over 60%. Composite synoptic circulations of the four types of MCSs showed several factors, including the locations and intensities of cyclones in the Bay of Bengal and high pressure in the Indochina Peninsula in the low-to-middle troposphere, and vortexes or southwesterly winds in the low-level troposphere, regulate the location and intensity of convection.