江苏省龙卷发生特征及其在年际尺度上与ENSO的关系研究

The characteristics of the occurrence of tornado in Jiangsu Province and its relationship with ENSO

利用1976-2005年江苏省龙卷信息化资料和高分辨率再分析资料,对江苏省龙卷的发生特征以及ENSO事件对江苏省龙卷发生数的影响进行了分析。结果表明:(1)1976-2005年,江苏省龙卷发生数年际和年代际变化明显,空间分布不均匀:1990s龙卷发生数较多;盐城南部和南通沿海地区是龙卷较为多发的区域。(2)ENSO事件对江苏省龙卷的发生频率有重要影响:ENSO冷事件月份平均龙卷发生数多于暖事件月份;非ENSO事件月份平均龙卷发生数居中。(3)ENSO冷事件时西南低空急流发生频率明显增加,由于低空急流增强而引起的江苏省地区水汽供应、动力条件和不稳定能量的分布均有利于龙卷的发生,导致在ENSO冷事件情况下江苏省龙卷发生数偏多。

The tornado data in Jiangsu Province and high resolution reanalysis dataset were used to investigate the characteristics of tornado occurrence and the influence of ENSO events on the tornado in Jiangsu Province.Results show that:(1)the occurrence of tornado has significant annual and inter⁃decadal variation as well as spatial differences.Tornado occurred more in 1990s,moreover,the south of Yancheng and the coastal region of Nantong are the main regions of high occurrence of tornado.(2)The ENSO events have significant influence on the occurrence of tornado in Jiangsu Province.During negative ENSO phases,the number of tornado exceeds positive phases and in non⁃ENSO period,the occurrences of tornado in Jiangsu is between positive and negative ENSO phases.(3)The number of southwesterly low⁃level jet are higher in negative ENSO events leading to stronger water supply and instable energy with the more advantageous dynamic characteristics,which has a positive impact on the occurrence of tornado.