Research group of Zhiyong Meng
Tornadoes in tropical cyclones (TCs) are more intense vortices than their parent TCs. The local strong winds produced by TC tornadoes may cause more severe injuries and deaths than TCs. Most tornadic TCs often cause several to tens, even more than a hundred of tornadoes. Currently, a systematic analysis of historical TC tornadoes in contiguous China has been missing, which restricts to some extent the risk assessment of TC tornadoes in China. This work established a quality-controlled dataset of TC tornadoes in China from 2006 to 2018, based on multiple sources of information, and examined their key environmental parameters. Results show that about one-third of the landfalling TCs in China were tornadic, and they produced 64 cataloged TC tornadoes with an average of five per year. TC tornadoes preferentially formed in the afternoon shortly before and within about 36 h after landfall of the TCs. These tornadoes mainly occurred in coastal areas with relatively flat terrains with the maximum number of TC tornadoes occurring in Jiangsu and Guangdong Provinces. Most of the TC tornadoes were spawned within 500 km from TC centers. Results also show that TC tornadoes in China tend to be spawned in an environment with large low-level storm relative helicity and large convective available potential energy taking entrainment effects into account, mainly in the northeast quadrant (Earth-relative coordinates) rather than the right-front quadrant (TC motion-relative coordinates) of the parent TC circulation. Most tornadoes were produced by TCs with a relatively weak intensity (tropical depressions/storms) in China, in contrast with those in the United States where most tornadoes are associated with stronger TCs. In addition, TC tornadoes were particularly active in 2018 in China, with 24 reported tornadoes accounting for 37.5% of the total surveyed samples from 2006-2018. The first recorded tornado outbreak in the modern history of China occurred in the envelope of TC Yagi (2018), in which 11 tornadoes were reported in association with significant midlevel intrusions of dry air and the interaction of Yagi with an approaching midlatitude midlevel trough.
Fig.1 Locations of TC tornadoes (red dots) in China from 2006 to 2018. The region around the Pearl River Delta is enlarged in the upper-left corner. Terrain heights (shaded) are also shown for reference.