广西一次持续性暴雨过程中低空急流的作用及其特征  

The role and characteristics of low-level jet during a persistent rainstorm in Guangxi

作　　者：覃皓 刘乐 农孟松 黄伊曼 屈梅芳 QIN Hao;LIU Le;NONG Mengsong;HUANG Yiman;QU Meifang(Guangxi Meteorological Observatory,Nanning 530022)

机构地区：[1]广西壮族自治区气象台,南宁530022

出　　处：《暴雨灾害》2023年第6期640-647,共8页Torrential Rain and Disasters

基　　金：广西自然科学基金项目(2023GXNSFBA026340,2022GXNSFBA035565);广西气象科研计划项目(桂气科2021Z03)。

摘　　要：2022年广西遭遇新中国成立以来最强“龙舟水”,其中6月17—22日的持续性暴雨过程累积雨量大、落区重叠,导致洪涝、山洪及滑坡等灾害。利用多源观测资料及欧洲中期天气预报中心ERA5再分析资料,分析了此次持续性暴雨过程中低空急流的影响及其特征,结果表明:(1)夜间低空急流明显增强,对流系统在急流核北侧发展,而日间随着低空急流减弱,对流系统也逐渐减弱,造成强降水主要集中于夜间。(2)夜间850 hPa低空急流左侧正涡度区与925 hPa边界层急流出口区在桂东北一带重合,配合桂北山脉地形阻挡形成深厚的低层辐合,有利于桂东北上升运动增强及对流系统不断发生发展。同时,大气低层对流不稳定迅速增大,为持续性暴雨提供了有利的不稳定层结环境。(3)低空急流的演变可用惯性振荡机制来解释。日间桂中至桂南地区地表被加热导致湍流摩擦逐渐增强,造成急流减速,具有次地转特征。夜间湍流摩擦作用减弱,急流加速并逐渐呈现出超地转特征。科氏力对非地转风的作用是造成急流动量增长的主要原因,而摩擦耗散、垂直输送等过程为急流动量汇。In 2022,Guangxi experienced the strongest Dragon Boat Precipitation since the founding of the People’s Republic of China.The persistent rainstorm process from 17 June to 22 June 2022 had large accumulations and overlapping falling areas,leading to floods,torrential floods,landslides,and other disasters.The impacts of the low-level jet and its characteristics during this process were analyzed based on multi-source observation data and ERA5 reanalysis data.The results show that:(1)The low-level jet enhanced significantly during the night,and the convective system developed on the north side of the jet core.During the daytime,the low-level jet weakened and the convec⁃tive system gradually disappeared,resulting in the heavy precipitation being mainly concentrated during the night.(2)During the night,the positive vorticity zone on the left of the 850 hPa low-level jet coincided with the exit zone of the 925 hPa boundary-level jet in the northeast of Guangxi,which combined with the mountain terrain barrier,and caused deep low-level convergence.The low-level convergence was con⁃ducive to the enhancement of the upward movement in northeast Guangxi and favored the continuous development of the convective system.At the same time,the convective instability in the lower atmosphere also increased rapidly,which provided a favorable unstable stratification environment for heavy precipitation.(3)The variation of the low-level jet can be well explained by the inertial oscillation mechanism.During the day,the surface heating in the central and southern regions of Guangxi led to the gradual enhancement of turbulent friction,resulting in jet deceleration with the characteristics of sub-geostrophic.During the night,the turbulent friction was weakened,and the jet accelerated,which gradually presented the characteristics of super-geostrophic.The Coriolis force acting on ageostrophic wind was the main contributor to the momentum of the jet,while friction dissipation and vertical transport were the momentum sinks.

关 键 词：持续性暴雨 低空急流 惯性振荡 非地转风 

分 类 号：P4321.1[天文地球—大气科学及气象学]