A Preliminary Study on the Organizational Modes of Mesoscale Convective Systems Associated With Warm-Sector Heavy Rainfall in South China

This work examines the organizational modes of mesoscale convective systems (MCSs) associated with warm-sector heavy rainfall events in South China based on composite radar reflectivities during April-June from 2007 to 2020. The results showed that these MCSs can be classified into the nonlinear mode (NL) and eight linear modes: trailing stratiform precipitation (TS), no stratiform precipitation (NS), leading stratiform precipitation (LS), parallel stratiform precipitation (PS), embedded lines (EL), bow echoes (BE), training line/adjoining stratiform (TL/AS), and multiple rain bands (MRB). The NL mode accounts for 40% of the total, while linear modes account for 60%, with the TS mode being the most frequent linear mode. The detailed features of the top three most frequent organizational modes (NL, TS, and NS) were examined in this work. First, the MCSs of the top three organizational modes have different formation modes. Eighty-four percent of NL systems and 77% of TS systems form via the broken areal mode, while 83% of NS systems form via the broken line mode. Second, relative to TS and NS systems, NL systems develop faster and have shorter lifespans but slower movements with higher 3-h and 6-h maximum precipitation values. Third, environmental analysis indicates that the Total Totals index (TTI) is significantly different among all the top three organizational modes, with the highest value in TS mode and the lowest value in NS mode. These features are apparently different from their counterparts in central East China due to different synoptic environments.