《海洋预报》| 广西东南部群发地质灾害区夏季极端降水及环流特征分析

摘要：基于广西东南部11次群发地质灾害数据、地面气象站小时降水数据和ERA5再分析资料，通过合成分析、水汽收支诊断及HYSPLIT后向轨迹追踪等方法，系统分析了该区域夏季极端降水、大气环流及水汽输送特征。结果表明：极端降水对桂东南群发性地质灾害的发生起到至关重要的作用，是灾害事件发生的必要条件。桂东南群发地质灾害发生前，区域平均连续降雨日数（时长）为7.4天（17.7 h），平均日（小时）最大降雨量为236.7 mm(56.0 mm)。根据影响天气系统差异，桂东南区域性极端日降水事件可分为台风型和高空槽-副热带高压型两类；区域性极端小时降水存在显著日变化特征，多发生于凌晨（01—04时）、早晨（07—09时）和午后（14—19时）3个时段，对应的主要影响系统分别为台风、高空槽-副热带高压型和大陆暖低压。水汽收支诊断结果表明，低空925 hPa偏南气流的水汽输送对桂东南的极端降水有重要贡献。热带印度洋中东部海域是桂东南极端降水事件最重要的水汽源地，西太平洋副热带高压和低空西南季风气流共同主导水汽向桂东南地区的输送过程。

关键词：桂东南;群发地质灾害;极端降水;环流特征;水汽输送

Abstract：In recent years, the southeastern Guangxi has experienced 11 cluster-triggered geological hazard events induced by extreme heavy rainfall during summer, resulting in severe casualties and economic losses. The characteristics of summertime extreme precipitation and the associated atmospheric circulation patterns in this region warrant further attention. Therefore, based on the data of 11 cluster geological disasters, hourly precipitation from surface weather stations and ERA5 reanalysis data, this paper analyzes the characteristics of cluster geological disasters induced extreme precipitation, circulation, and water vapor transportation in the southeastern Guangxi by composite analysis, water vapor budget, and HYSPLIT backward trajectories. Results show that extreme precipitation is a crucial factor in the occurrence of cluster geological disasters in southeastern Guangxi, serving as a necessary condition for these events. On average, the continuous rainfall days(hours) before the occurrence of geological hazards in the southeastern Guangxi is approximately 7.4 days(17.7 hours), with an average daily(hourly) maximum rainfall of 236.7 mm(56.0 mm). Based on the influencing weather systems, regional extreme daily precipitation events are categorized into two types: typhoon-related and upper trough-subtropical high-related. Regional extreme hourly precipitation events exhibit significant diurnal variations, frequently occurring before dawn(01:00—04:00), early morning(07:00—09:00), and afternoon(14:00—19:00). These events are associated with distinct weather systems, namely typhoons, upper trough-subtropical highs, and continental warm lows, respectively. Water vapor budget diagnostics reveal that water vapor from southerly flow at the 925 hPa is vital for extreme precipitation in this region. And the central and eastern tropical Indian Ocean is identified as the primary water vapor source by the HYSPLIT model. Additionally, the western North Pacific subtropical high and low-level southwestern monsoon flow significantly contribute to the redirection of water vapor towards the southeastern Guangxi.

Key words：southeastern guangxi; cluster geological disasters; extreme precipitation; circulation characteristics; water vapor transportation

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