2022年广西“龙舟水”暖区暴雨中低空急流的日变化机制  

Diurnal variation mechanism of low-level jet during the dragon-boat warm-sector rainstorm process in 2022 in Guangxi

作　　者：覃皓 农孟松 邱滋 祁丽燕 Qin Hao;Nong Mengsong;Qiu Zi;Qi Liyan(Guangxi Meteorological Observatory,Nanning 530022,China)

机构地区：[1]广西壮族自治区气象台,南宁530022

出　　处：《气象研究与应用》2023年第1期20-25,共6页Journal of Meteorological Research and Application

基　　金：广西气象科研计划项目(桂气科2022QN08);广西自然科学基金项目(2022GXNSFBA035565);广西壮族自治区气象局短时临近天气预报技术创新团队项目。

摘　　要：利用多源资料,选取2022年广西“龙舟水”期间6月3—4日暴雨过程,进行暖区暴雨中低空急流的日变化机制分析。结果表明:(1)过程期间低空急流在日间减弱而在夜间至次日凌晨加强。夜间在低空急流顶端附近不断有对流系统发生发展,造成桂东北暖区强降水。(2)低空急流日变化可由惯性振荡机制解释。日间非地转风方向与背景风大致相反,使得低空急流减弱,全风速为次地转;夜间非地转风顺时针旋转为西南风,与背景风场叠加导致全风速出现超地转,使得低空急流增强。(3)动量方程诊断表明,低涡东移而副高维持的形势使得过程期间维持较强背景地转风。日间湍流摩擦及平流作用导致低空急流逐渐减弱;夜间科氏力和气压梯度力间的不平衡所导致的非地转过程驱动了低空急流发展增强。Based on multi-source data,the diurnal variation mechanism of the low-level jet in the warmsector rainstorm process is analyzed by selecting the process of heavy rainfall from June 3 to 4 during the dragonboat rainy period in Guangxi in 2022.The results showed that(1)During the process,the low-level jet weakens during the day and strengthens during the night to the early morning of the next day.At night,the convective system develops continuously near the top of the low-level jet stream,resulting in a warm-sector rainstorm in northeast Guangxi.(2)The diurnal variation of the low-level jet can be explained by the inertial oscillation mechanism.The direction of the ageostrophic wind in the daytime is opposite to the background wind,which weakens the low-level jet and the total wind speed is subgeostrophic.At night,the ageostrophic wind rotates clockwise to the southwest wind,superimposes with the background wind field and causes the total wind supergeostrophic,which enhances the low-level jet.(3)The momentum equation diagnosis shows that strong background geostrophic wind is maintained during the process due to the eastward movement of the low vortex and the maintenance of the Western Pacific subtropical high.The turbulent friction and advection in the daytime cause the low-level jet weakens gradually.The ageostrophic process caused by the imbalance between the Coriolis force and the pressure gradient force at night drives the development and enhancement of the low-level jet.

关 键 词：低空急流 日变化 惯性振荡 非地转风 动量方程 

分 类 号：P426.62[天文地球—大气科学及气象学]