The characteristics of mesoscale convective systems generated over the Yunnan-Guizhou Plateau during the warm seasons

The characteristics of mesoscale convective systems (MCSs) over the Yunnan-Guizhou Plateau (YGP) during the warm seasons (April-August) are investigated using an automatic tracking algorithm based on long-term (2000-2018) hourly geostationary satellites data of temperature of black body. A total of 1,845 MCSs generated over the YGP are identified and further classified into the eastward moving type (EMT; similar to 13.1%) and noneastward moving/dissipating type (NDT; similar to 86.9%). The two types of MCSs exhibit varying characteristics. The EMTs are mainly active in the eastern flank of the YGP with a longer mean lifespan (similar to 16.5 hr), while the NDTs occur anywhere over the YGP with a preference for the central YGP with a shorter mean lifespan (similar to 7.6 hr). The MCSs are observed most frequently during June-July, while the ratio of EMTs reaches the highest in April due to the strongest steering flows. The abundant moisture supply plays a vital role in the generation and development of MCSs in June, whereas the dynamic forcing and high CAPE are favourable to MCSs in July. In terms of the diurnal cycle, the NDTs are generally initiated in the afternoon, reach mature in the late afternoon, and dissipate at night. By contrast, the mature stage of EMTs shows double diurnal peaks in the late afternoon and early morning. The MCSs are usually generated in an instable environment accompanied by strong vertical wind shear and intense low-level water vapour flux over the YGP, and the MCSs tend to vacate the YGP with strong mid-level westerlies and instable environment in the downstream regions. Compared to MCSs in Tibetan Plateau, the ratio of the EMTs is higher with longer lifespans though fewer MCSs are generated over the YGP.