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2023年6月1日辽宁龙卷风暴环境及演变特征分析

Environmental Conditions and Evolutionary Characteristics of the Tornadic Storms in Liaoning Province on June 1 2023

  • 摘要: 利用多源观测和ERA5再分析资料,本文详细分析了2023年6月1日阜新EF1级和开原EF2级龙卷风暴的环境条件、演变特征和龙卷形成的可能机制。结果表明:辽宁位于东北冷涡西南象限和高空槽南侧,地面(或850 hPa)与500 hPa的强垂直减温率是造成本次过程的极端环境条件因子。阜新龙卷风暴具有钩状回波、下沉反射率因子核(DRC)和龙卷涡旋特征(TVS),由干线上生成的两个孤立风暴合并而成;其东侧强回波产生1小时降温超过6℃的强冷池,冷池出流与干线交汇,在强冷池的边缘形成三汇点;当钩状回波移到三汇点时,不太强的下沉气流产生强度适宜的冷池,加之三汇点处强辐合抬升的共同作用,在DRC和TVS下方生成龙卷。开原龙卷风暴为线状对流系统,是沿着地面辐合线上传播的多个风暴合并而成;由于开原位于低空急流内并具有更强的低空风切变,有利于地面辐合线上首先出现微气旋;微气旋的西侧风暴产生1小时降温达到10℃的冷池,其出流与地面辐合线交汇也形成了三汇点,但开原的辐合显著强于阜新;当微气旋经过三汇点时,在强辐合拉伸作用下,低层旋转达到生命期最强且首次达到TVS标准时,其下方产生龙卷。本次东北冷涡过程具有极端条件不稳定条件,由干线和辐合线上生成的风暴在龙卷生成区30 km附近区域产生强冷池,在强冷池边缘、地面1小时降温小于4℃的区域,改善了大气低层湿度条件,还形成三汇点加强了地面辐合,当TVS或微气旋经过这些三汇点时分别形成龙卷。

     

    Abstract: Based on multi-source observations and ERA5 reanalysis data, we present in detail the environment conditions, storm evolution and possible formation mechanisms of the Fuxin EF1 tornado and the Kaiyuan EF2 tornado on June 1 2023 in this paper. The results show that the northern part of Liaoning Province was affected by the upper trough and lower-level shear line at the rear part of a Northeast China Cold Vortex. The strong vertical temperature lapse rate between the surface (or 850 hPa) and 500 hPa was the extreme environmental condition factor that caused this process. The Fuxin tornado storm had hook echo, descending reflectivity core (DRC) and tornado vortex signature (TVS), formed by the merger of two isolated storms generated on the dry-line. The strong echo on the east side of tornado storm generated the strong cold pool with the surface temperature dropped by more than 6 ℃ within one hour. The outflow of cold pool merged with the dry-line, forming a triple point at the edge or the strong cold pool. When the hook echo moved to the triple point, a moderately strong downdraft produced a cold pool with suitable intensity, coupled with the strong convergence and uplift at the triple point, the tornado generated under the DRC and TVS. The Kaiyuan tornado storm was a linear convective system, formed by the merger of multiple storms along the surface convergence line. Due to Kaiyuan"s location within the low-level jet and its stronger low-level wind shear, it was conducive to the initial formation of a misocyclone on the ground convergence line. The cold pool with a temperature dropped by more than 10°C within an hour was produced by the storm at the west side of the misocyclone. The cold pool outflow merged with the surface convergence line to form a triple point, resulting in stronger convergence in Kaiyuan than that of Fuxin. When the misocyclone passed through the triple point, under the strong convergence and stretching effect, the low-level rotation of misocyclone reached its strongest in the life cycle which first met the TVS standard and the Kaiyuan tornado generated. The Northeast cold vortex process had extreme conditions of instability, the storms generated on the dry-line and surface convergence line, produced a strong cold pool within an area of about 30 km near the tornado genesis zone. At the edge of the strong cold pool where the ground temperature dropped less than 4°C within an hour, the humidity conditions of the lower atmosphere were improved. The triple point was also formed to strengthen the ground convergence. When the TVS or the misocyclone passed through these triple confluence points, tornadoes were formed respectively.

     

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