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气象:2020,46(5):589-602
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2019年7月3日辽宁开原EF4级强龙卷形成条件、演变特征和机理
郑永光,蓝渝,曹艳察,张小玲,陈传雷,朱文剑,张小雯,关良,盛杰,唐文苑,周晓敏,杨波,张涛,方翀
(国家气象中心,北京 100081; 辽宁省气象灾害监测预警中心,沈阳 110052)
Environmental Conditions, Evolution and Mechanisms of the EF4 Tornado in Kaiyuan of Liaoning Province on 3 July 2019
ZHENG Yongguang,LAN Yu,CAO Yancha,ZHANG Xiaoling,CHEN Chuanlei,ZHU Wenjian,ZHANG Xiaowen,GUAN Liang,SHENG Jie,TANG Wenyuan,ZHOU Xiaomin,YANG Bo,ZHANG Tao,FANG Chong
(National Meteorological Centre, Beijing 100081; Liaoning Meteorological Disaster Monitoring and Warning Center, Shenyang 110052)
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投稿时间:2019-08-15    修订日期:2020-02-11
中文摘要: 综合应用高时空分辨率多源观测资料,分析了2019年7月3日下午辽宁开原EF4级强龙卷的天气形势、环境条件、对流触发、对流风暴演变特征和龙卷的形成与消亡机制。开原龙卷发生在东北冷涡西南侧500 hPa西北气流、850 hPa切变线、地面强西南暖湿气流中;除了对流层中下层相对湿度低、抬升凝结高度较高是开原龙卷的不利环境条件外,其他有利于强中气旋龙卷的环境条件都具备。但风廓线雷达观测和天气雷达观测的径向速度场显示0~1 km垂直风切变的增强具有中尺度特征,表明边界层强风与中层急流相耦合形成了非常有利于龙卷的垂直风切变条件。形成开原龙卷的直接系统是一孤立超级单体,具有典型的超级单体雷达回波特征、强中气旋和龙卷涡旋特征等;其由地面干线辐合线与东侧的阵风锋辐合线共同作用触发。该对流风暴前部产生的降水先使得开原及周边地区大气快速饱和、显著改善了大气低层湿度条件,当对流风暴后部钩状回波部分移动到该区域时,有利于其不太强的下沉气流产生强度适宜的冷池,加之边界层强暖湿气流入流、强低层和中层垂直风切变与强烈上升气流的共同作用,从而产生了该次开原龙卷。地面自动站观测温度分布表明,开原龙卷超级单体的冷池与环境大气温度差异在2~4℃时有利于龙卷形成,而当对流风暴的强下沉气流使冷池温差加大到7℃时,不利于近地面垂直涡度维持,导致龙卷消亡。
Abstract:Based on multi-source observations with high spatio-temporal resolution, we present in detail the synoptic situation, environmental conditions, triggering and evolution characteristics of the convective storm, and formation and demise mechanisms of the EF4 tornado in Kaiyuan, Liaoning Province on the afternoon of 3 July 2019 in this paper. The Kaiyuan tornado occurred under the 500 hPa northwesterly airflow and the 850 hPa shear line in the southwest side of a cold vortex over Northeast China, and in the strong warm and moist southwesterly airflow at the surface. Except for the low relative humidity in the middle and lower troposphere and the higher lifting condensation level which were unfavorable for the tornado, other favorable environmental conditions for mesocyclonic tornado were all satisfied. However, winds of the Shenyang wind-profiling radar and radial velocity of Shenyang weather radar both show that the enhanced 0-1 km vertical wind shear had a mesoscale feature indicating that the coupling between the boundary layer jet and the mid-level jet formed strong vertical wind shear favorable for the EF4 tornado. The Kaiyuan tornado was generated by an isolated supercell with typical supercell radar echo features, an intense mesocyclone and tornadic vortex signature, etc. The strom was triggered by both a dryline and a convergence line of gust front to the east of the dryline. The rainfall produced in the front of the storm first made the atmosphere rapidly saturated over Kaiyuan and its vicinity. When the hook echo part at the back of the storm moved to Kaiyuan and its vicinity, the significantly improved low-level moisture condition was good for the less strong downdraft of the storm to generate the cold pool with suitable intensity. So the storm, with the suitable cold pool, strong warm and moist boundary-layer air inflow, strong low-level and mid-level vertical wind shear, and intense updraft, produced the EF4 tornado in Kaiyuan. The temperature distribution from automatic weather stations shows that the temperature differences between cold pool of the storm and the ambient atmosphere were 2-4℃, favorable for Kaiyuan tornadogenesis. While the strong downdraft of the storm produced the intense cold pool with the temperature difference up to 7℃ from the environmental atmosphere, it destroyed the maintenance of vertical vorticity near the ground and then caused the demise of the Kaiyuan tornado.
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基金项目:国家重点研发计划(2018YFC1507504和2017YFC1502003)和国家自然科学基金项目(41375051)共同资助
引用文本:
郑永光,蓝渝,曹艳察,张小玲,陈传雷,朱文剑,张小雯,关良,盛杰,唐文苑,周晓敏,杨波,张涛,方翀,2020.2019年7月3日辽宁开原EF4级强龙卷形成条件、演变特征和机理[J].气象,46(5):589-602.
ZHENG Yongguang,LAN Yu,CAO Yancha,ZHANG Xiaoling,CHEN Chuanlei,ZHU Wenjian,ZHANG Xiaowen,GUAN Liang,SHENG Jie,TANG Wenyuan,ZHOU Xiaomin,YANG Bo,ZHANG Tao,FANG Chong,2020.Environmental Conditions, Evolution and Mechanisms of the EF4 Tornado in Kaiyuan of Liaoning Province on 3 July 2019[J].Meteor Mon,46(5):589-602.