The characteristics of summer mesoscale convective systems with different moving paths over Southwest China

Employing an iterative rain-cell tracking approach with the products of Temperature of Black Body at cloud top observed by the Fengyun-2 meteorological satellites, we investigate the characteristics of mesoscale convective systems (MCSs) over southwest China (SWC) during the summer of 2015-2020. MCS initiation locations, precipitation centers and great contribution to the total rainfall amount predominantly situated along the Hengduan Mountains, the eastern slope of Tibetan Plateau, the southern edge of the Yunnan-Guizhou Plateau, and the southern coastal areas. The phase of precipitation diurnal cycle displays notable regional differences over SWC, with a pronounced eastward propagation and a less distinct westward propagation along 22 degrees-26 degrees N. Then the MCSs are identified and grouped as the westward-moving MCSs (WM-MCSs) and eastward-moving MCSs (EM-MCSs) to investigate characteristics of MCSs with different moving paths. WM-MCSs (EM-MCSs) are more frequently originated in the southern (northern) regions of SWC. WM-MCS precipitation prefers to peak in the afternoon, especially over the regions east of 108 degrees E, while the EM-MCS precipitation tends to peak during nocturnal hours, with a distinct eastward delay north of 24 degrees N. EM-MCSs tend to have longer durations and moving distances, while the cloud cluster coverage for WM-MCSs decreases more rapidly after reaching maturity, and exhibits higher cloud tops initially but sustain for a shorter duration. The easterly (westerly) anomaly of wind at 500 hPa favors the westward (eastward) movement of WM-MCSs (EM-MCSs). When WM-MCSs (EM-MCSs) initiate, the westerly jet on the northern side of the South Asian High is weaker (stronger). For EM-MCSs, the warm anomaly around 250 hPa is conducive to the divergence of the upper-level troposphere.