覃皓,农孟松,翟丽萍,李佳颖,张惠景,蓝盈,黄晴,邱滋,黄明华. 2024. 广西沿海“23.6”弱热带低压破纪录暴雨过程的诊断分析. 气象学报,82(3):289-305. DOI: 10.11676/qxxb2024.20230121
引用本文: 覃皓,农孟松,翟丽萍,李佳颖,张惠景,蓝盈,黄晴,邱滋,黄明华. 2024. 广西沿海“23.6”弱热带低压破纪录暴雨过程的诊断分析. 气象学报,82(3):289-305. DOI: 10.11676/qxxb2024.20230121
Qin Hao, Nong Mengsong, Zhai Liping, Li Jiaying, Zhang Huijing, Lan Ying, Huang Qing, Qiu Zi, Huang Minghua. 2024. Diagnostic analysis of the June 2023 record-breaking rainstorm process caused by a weak tropical depression in Guangxi coastal. Acta Meteorologica Sinica, 82(3):289-305. DOI: 10.11676/qxxb2024.20230121
Citation: Qin Hao, Nong Mengsong, Zhai Liping, Li Jiaying, Zhang Huijing, Lan Ying, Huang Qing, Qiu Zi, Huang Minghua. 2024. Diagnostic analysis of the June 2023 record-breaking rainstorm process caused by a weak tropical depression in Guangxi coastal. Acta Meteorologica Sinica, 82(3):289-305. DOI: 10.11676/qxxb2024.20230121

广西沿海“23.6”弱热带低压破纪录暴雨过程的诊断分析

Diagnostic analysis of the June 2023 record-breaking rainstorm process caused by a weak tropical depression in Guangxi coastal

  • 摘要: 利用多源观测资料及ERA5再分析资料,基于大气热、动力诊断方程,对2023年6月7—9日广西沿海破纪录热带低压暴雨过程的成因及低压维持的可能机制进行了分析,结果表明:(1)在中高纬度与低纬度天气系统相互作用背景下,热带低压在广西境内盘旋少动,促成了此次强降水过程。期间大气热力、水汽因子均伴有显著异常,整层水汽通量散度、大气可降水量及K指数标准化异常分别达到−5.5、3.2、1.3。(2)降水最强时段集中于夜间至凌晨,准静止的中尺度对流云团以及对流系统“列车效应”使降水不断在局地累积,造成破纪录累计雨量。(3)7日(8日)夜间至8日(9日)凌晨,热带低压东南侧(东侧)暖式切变线(边界层急流)以及陆面摩擦为强降水的发生、发展提供了动力条件。9日边界层急流辐合强于8日切变线辐合,锋生强迫更强。热带低压系统增强导致的气压梯度力增大以及位势高度经向平流对应的气压梯度力做功过程促进了局地动能增长,是边界层急流发展的原因。(4)热带低压环流不断将中国南海水汽卷入其内部,水汽辐合及垂直输送使得湿层不断增厚,有利于降水率增大。持续的暖湿气流输送有利于不稳定层结维持,使大气低层对流不稳定结构贯穿整个降水过程。其中,风垂直切变和大气斜压性的有利配置使得9日层结不稳定特征较8日更强,与动力条件相结合促使9日出现更强降水。(5)热带低压系统维持主要受水平风场辐合效应支撑,地转风分量在整个过程中贡献相对较弱,非地转风分量的水平散度项主导了局地涡度变化,与非地转风惯性旋转后向热带低压中心辐合有关。

     

    Abstract: Based on atmospheric thermal and dynamic diagnostic equations, the cause of the record-breaking tropical depression rainstorm process in the coastal area of Guangxi and the possible mechanism of the maintenance of the depression during 7—9 June 2023 are analyzed using multi-source observations and ERA5 reanalysis data. The results are as follows: (1) Under the background of the interaction between the mid- and high-latitude and low-latitude weather systems, the tropical depression moved slowly and even remained stationary over Guangxi, which contributed to the occurrence of the heavy precipitation process. The atmospheric thermal elements and water vapor content showed significant anomalies during the process. Normalized anomalies of the divergence of vertically integrated vapor flux and precipitable water and K index reached −5.5, 3.2 and 1.3, respectively. (2) Precipitation is strongest from night to early morning. The quasi-stationary mesoscale cloud clusters and the "echo training" in the convective system caused continuous local accumulation of precipitation and resulted in record-breaking rainfall. (3) From the night of 7 (8) June to the early morning of 8 (9) June, the warm shear line (boundary layer jet) to the southeast (east) of the tropical depression and land surface friction provided the dynamic condition for the occurrence and development of heavy precipitation. The convergence of the boundary layer jet on 9 June was stronger than that of the shear line on 8 June, and the frontogenetical forcing was stronger. The increase in pressure gradient force caused by the strengthening of tropical depression system and the pressure gradient force impact caused by meridional advection of potential height promoted the growth of local kinetic energy, which is the reason for the development of boundary layer jet. (4) The tropical depression circulation continuously sucked water vapor from the South China Sea, and the convergence and vertical transport of water vapor increased the wet layer depth, which is conducive to the increase of precipitation efficiency. Continuous warm and moist airmass transport was conducive to the maintenance of unstable stratification, and the convective unstable structure in the lower atmosphere maintained throughout the whole process. The configuration of vertical wind shear and atmospheric baroclinicity made the stratification more unstable on 9 June than that on 8 June, which, combined with the dynamic conditions, led to more intense precipitation on 9 June. (5) The maintenance of the tropical depression system was mainly supported by the convergence of horizontal winds. The contribution of the geostrophic wind component is relatively weak in the whole process, while the horizontal divergence term of the ageostrophic wind component led to changes in local vorticity. This is related to the convergence in the tropical depression center after the inertia rotation of the ageostrophic wind.

     

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