Abstract:
By using Doppler weather radar data of Pu’er and Wenshan, the FY-2G satellite cloud image data, combined with the NCEP reanalysis data and the live weather data, two tornado weather events happened on May 12, 2017 and May 31, 2021 in Menghai and Guangnan were analyzed. The results show that both tornadoes occurred in flat dam which were surrounded by high mountains, and reservoirs were also found nearby the place where tornado occurred. On the ground map, the vortex triggered by the updraft encountering the surface convergence line caused the two non-supercell tornadoes. When tornado weather occurred, the drop of air pressure was accompanied by the.decrease of temperature. On T-lnP diagram, the vertical humidity profile showed “Dry-Moist-Dry” structure, the CAPE for the two events were 1676.3 and 2074.2 J·kg
−1 respectively, and the maximum vertical wind shear of 0~3 km was 11.1 m·s
−1. Thus in the areas above Menghai and Guangnan, an absolutely unstable atmospheric stratification was formed, which further provided the favorable backgrounds for the formation of tornadoes. The satellite cloud images showed that the two tornado events were both triggered by mesoscale convective clusters, and the TBB gradient was large over the regions where the tornadoes were observed. Besides, the coupling of low-level cyclonic circulation and high-level divergence was observed during the two tornado events on the radar charts.