Characteristics of Spatio-Temporal Distribution and Storm Morphologies of Tornadoes in Jiangsu Province
Based on the climate impact assessment documents, significant weather reports, tornado disaster records from Jiangsu civil affairs department and other relevant data from 2006 to 2018, the spato-temporal distribution, strength distribution, weather background and storm morphology characteristics of the Jiangsu tornadoes are analyzed according to the “Enhanced Fujita Scale”. The main results show that there were 41 tornadoes recorded in 27 tornadic days during the 13 years (2006-2018) with an average annual tornado of 3.2 times, of which the tornado events at EF2 level occurred the most, accounting for 39%, while the EF4 tornado was only recorded once, referring to the 23 June (6·23) Funing severe tornado. Since the 21st Century, there has been no record of extreme tornado events of EF5 level in Jiangsu Province, while the weak tornadoes of EF0 and EF1 are likely to be ignored due to the weak disaster, so their statistical results may be significantly underestimated. Tornadoes mainly occur in the eastern coastal area, the central coastal area and the western area of the north of the Huaihe River. Compared with the past, the high-risk center of tornado in central Jiangsu has a trend of moving southward, while the high-risk center in the eastern coastal area shows a feature of northward movement. Yancheng, Xuzhou and Yangzhou are the high frequency cities of tornado, but no tornado has happened in Suqian, Lianyungang, Changzhou and Zhenjiang in recent years. Most tornadoes occur in spring and summer, 90% of which are seen in July and August. The onset of tornadoes is from 10:00 BT to 20:00 BT, and 78% of tornado genesises in the diurnal variation are between 15:00 BT and 20:00 BT. About 50% of the tornadoes occur during the Meiyu period, and 27% of them are typhoon tornadoes. Yancheng is the highest incidence area of tornadoes in Meiyu period, and the Yangzhou-Taizhou Region has high incidence of tornadoes in mid-summer. There is no obvious high-risk area of typhoon tornadoes in Jiangsu. More than 50% of tornadoes in Jiangsu are generated in supercell mesocyclone embedded in cluster convective morphology, and about 30% of tornadoes are produced in the quasi-linear convective system convective morphology. Contrast to high frequency of tornadoes produced by the discrete cells in the United States, the possibility of tornadoes generated from discrete cells in East China (mainly in Jiangsu Province) is the lowest, and only two tornadoes (less than 5%) were generated in discrete cells in the past 13 years.