摘要
Abstract
This study utilized conventional upper-air and surface observational data,ERA5 hourly reanalysis data(0.25 °×0.25 °),S-band dual-polarization radar data,and X-band phased-array radar data to analyze the circulation background,convective system evolution,and the causes of an extreme gale event that occurred in Zhejiang on July 25,2022.The results indicated that:(1)The extreme gale event occurred under the background of a shortwave trough moving eastwards around the Subtropical High,with favorable conditions such as abundant low-level water vapor,significant upper-level dry layers,and strong unstable stratification.The surface mesoscale convergence line played a pivotal role in triggering the event.(2)The extreme gale was caused by cell J0,whose intricate evolution was captured by the X-band phased-array radar and its wind field inversion.The vortex structure of J0 initially formed in the middle layer,then developed upwards and downwards,and finally weakened and disappeared from the lower to the upper layer,with significant convergence appearing in the middle layer.Vertically,after J0 formed,it merged with the cell behind it,converged with the low-level updraft atop the high reflectivity gradient zone,and formed a converging downdraft at its leading edge.(3)After J0 formed,it enhanced the surface cold pool and,upon merging with the cell behind it,strengthened the sinking airflow.When the airflow reached the ground,it further increased the wind speed under the influence of pressure gradient,which was the primary cause of the extreme gale.In addition,the negative buoyancy generated by the involvement of environmental dry air in the storm and the drag induced by precipitation particles also contributed to the gale's severity.关键词
极端大风/S波段双偏振雷达/X波段相控阵雷达/三维风场反演Key words
extreme gale/S-band dual-polarization radar/X-band phased-array radar/three-dimensional wind field inversion分类
大气科学
