双系统影响龙卷强对流环境场模拟研究
投稿时间: 2018-03-16  最后修改时间: 2018-04-15  点此下载全文
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作者单位E-mail
王坚红 南京信息工程大学海洋科学学院 1597706505@qq.com 
纪晓涵 南京信息工程大学大气科学学院  
王群 盐城市气象局  
苗春生 南京信息工程大学  
基金项目:国家自然科学基金面上资助项目(41276033);江苏科技支撑项目(BE2014729);江苏高校优秀学科建设工程项目(PAPD)
中文摘要:对2009-2016年江苏北部龙卷事件的环境场进行统计与诊断, 并对两次典型龙卷过程的环境场进行数值模拟, 重点探讨近海岸平原地区的江苏北部在春夏季节成为中国强龙卷最高频发生地的特殊性以及环境系统对龙卷环境场的增强机制。分析结果显示苏北龙卷主要发生在春夏季节,发生率占全省58.6%。其中盐城和徐州占比又分别达到64.7%和23.5%。春夏季节冷暖干湿气团势力相近, 天气系统尺度适中, 锋面系统多, 易发生多系统抗衡造成的局地强对流。 对盐城(2016年)和徐州(2009年)的两次典型龙卷强对流环境场分析显示, 盐城龙卷的环境场为锋面气旋和岸滨锋相遇,徐州龙卷的环境场为变形场锋生和海风锋汇合。WRF模拟结果显示,伴随双锋面系统的不同旋转方向的二级环流相遇,可造成局地风速垂直扭转,有利于驱动和增强局地正涡度成份; 双锋面二级环流垂直上升支的叠加, 可在平坦地区产生强烈的系统性抬升运动。扭转与抬升两种运动的合成效应, 将构建有利龙卷类强对流天气发生发展的环境场。而各种强对流指标可能需要依据局地统计特征进行参考使用。
中文关键词:苏北龙卷环境场, 海岸带系统,低层锋面系统,扭转与抬升增强的模拟
 
The Numeric Simulation Study on the Environment Fields of the Strong Convective Tornado under Two System Influence
Abstract:For investigating the particularity of high rate of strong tornado occurrence in Northern Jiangsu province during spring and summer and the excitation mechanism of tornado by environmental factors, the tornados in the Northern Jiangsu during 2009-2016 are analyzed by statistics and diagnostics, furthermore two typical tornado events are numerical simulated. The analysis results showed that the tornadoes of the northern area mainly occur in spring and summer and the incidence rate is 58.6% in whole province, at the cities of Yancheng and Xuzhou in the northern area their incidence rates are 64.7% and 23.5% respectively. The intensities of cold, dry and warm, wet air parcels are similar in spring and summer, so more front systems generating and existence, and the sizes of synoptic systems are medium, under such environment background the local strong convections are easily forced by countervailing multi systems. The diagnostic analysis of typical tornadoes at Yancheng in 2016 and at Xuzhou in 2009 show that the previous one is caused by the meet together of a frontal cyclone and coastal front and the second one is forced by the confluence of the deformation field frontogenesis and sea-breeze front. The numerical simulation of the two tornado events show that the vertical second circulations of the two front systems meeting each other with different rotation directions will cause the wind vertical torsion and force the local positive vorticity increase; the composition of vertical ascending motion of the second circulations will generate the systemic strong uplift force at flat land area. The both vertical torsion and strong uplifting together will provide and develop the environment fields to enhance the occurring conditions of strong convective tornado. When the various strong convective indexes are applied ,it may need to consider their local statistic features.
keywords:The environment field of tornado in Northern Jiangsu, the coast system, the frontal system at low level, the simulation of uplift and torsion conditions
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