Analysis of organization mode of the mesoscale convective systems during rainstorm days in Taishan mountain region

The organization mode and evolution characteristics of mesoscale convective systems (MCS) that cause heavy rain during rainstorm days in Taishan region are analyzed by using the new generation composite radar reflectivity data, satellite data and operational observation data from May to October during 2020—2022. The results show that the MCS in Taishan area can be divided into six identified classes: Nonline-MCS (NL), Embedded line MCS (EL1), Embedded lines MCS (EL2), Trailing stratiform MCS (TS), Training line MCS (TL) and Parallel stratiform MCS (PS), and four of them are the same as the previous classifyed archetype, but the EL2 and TL are the new statistical classes in Taishan region. On satellite cloud charts, the 6 classes often appear as irregular oval or long stripes, with the highest black body temperature (TBB) below -50°C, making it difficult to distinguish the detailed mode of MCS. However, the new generation of weather radar data can make up for this defect. According to the analysis, NL, EL1 and EL2 are the main classes affecting the Taishan region, accounting for 86% of the total sample, of which EL1 is the most. EL1 class, including the embedded line (EL) in existing research results and the convective lines without stratiform rainfall (NS) , generates its source in the area from Xingtai to Dezhou and Liaocheng, and moves mostly in a southeastern direction; the second is the NL, which generates in the Taishan area, with strong echoes dispersed and little movement; the third is the EL2 class, which generates in the area between Kaifeng and Hefei, and moves mostly in a northeastern direction after formation. Except the EL2 and PS, the other classes appear with a distinct diurnal variation, showing two peaks in the afternoon and at night. The intensity, shape, travel speed and direction of most MCS change when they pass over the Taishan Mountains, especially for TL and PS. According to statistics, only 12% of MCS mode do not change significantly, and the rest of the samples change every 1.5-3h. In contrast, NL is not only one of the main classes that cause heavy rain in Taishan area, but also an intermediate mode in the evolution of other MCS in many cases.