湘中地区夏季极端小时降水和极端降水事件的时空分布及其环流特征

Spatial and temporal distribution and circulation characteristics of extreme hourly precipitation and precipitation events in central Hunan during summer

摘要

为揭示湘中地区夏季极端降水事件的时空变化与形成原因，提升区域极端暴雨灾害防御能力，利用 2016-2025年夏季湘中地区 830 个气象观测台站逐小时降水资料及 ERA5 再分析资料，分析了该地区夏季极端小时降水和不同历时极端降水事件的时空分布特征，并比较了不同历时极端降水事件的异常环流特征。结果表明：(1) 湘中地区夏季极端小时降水的阈值、平均降水量和强度呈现“北高南低”的空间分布，阈值和强度高值中心集中在辰溪、麻阳和溆浦一带，平均降水量和平均频次大值区主要分布于雪峰山主体中段及其南麓地区；极端小时降水旬尺度高频区呈阶段性“自南向 北”演变特征。(2) 极端降水事件频次自西向东呈“少-多-少”分布，平均降水量则表现为“北多南少”格局，平均强度存在多个局地高值中心，安化、溆浦和长沙县的极端降水事件降水贡献率相对更高。(3) 短历时极端降水事件频次峰值时段在 8 月上中旬，中历时事件主峰在 6 月上旬、次峰在 6 月下旬，长历时事件高峰时段在 6 月下旬至 7 月上旬；短、长历时事件日变化表现为单峰型，峰值分别出现在 16 时和 08 时 (北京时，下同)，中历时事件呈双峰型，主峰在 16 时、次峰为 07 时。(4) 短历时极端降水事件发生在西太平洋副热带高压 (以下简称副高) 偏东、偏弱背景下，湘中至我国东南沿海为异常气旋性环流控制；中、长历时事件副高偏西、偏强，我国南海至华南地区为异常反气旋性环流，有利于孟加拉湾与南海的水汽输送至湘中地区。研究结果可为极端降水监测预警和灾害风险防范提供参考。

Abstract

Based on hourly precipitation observations from the National Meteorological Information Center of the China Meteorological Administration and ERA5 hourly 0.25°×0.25° reanalysis data during summer from 2016 to 2025, this study investigates the spatiotemporal evolution patterns and underlying mechanisms of extreme precipitation events in central Hunan region, in order to enhance the regional rainstorm disaster prevention ability. We analyze the spatiotemporal distribution of extreme hourly precipitation and extreme precipitation events in central Hunan, and compare the associated abnormal circulation characteristics for events of different durations. The results are as follows. (1) The threshold, mean precipitation, and intensity of extreme hourly precipitation in central Hunan during summer exhibits a “north–south contrast” with higher values in the north and lower values in the south. High-value centers for threshold and intensity are located in the Chenxi-Mayang-Xupu area, while the high-value areas of mean precipitation and mean frequency are along the central Xuefeng Mountain range and its southern foothills. The ten-day periods with high-frequency of extreme hourly precipitation exhibit a phased "south-to-north" progression. (2) The frequency of extreme precipitation events shows a "low-high-low" pattern from west to east, while the mean precipitation amount exhibits a "more in the north, less in the south" distribution, The mean intensity presents multiple localized maxima. and the contribution rates of extreme precipitation events to total precipitation are particularly prominent in Anhua, Xupu, and Changsha County. (3) The short-duration extreme precipitation events peak in early to mid-August; medium-duration events peak in early June followed by late June; long-duration events peak from late June to early July. The diurnal variation of short- and longduration events shows a unimodal pattern, peaking at 16:00 and 08:00 (Beijing time) respectively, while medium-duration events exhibit a bimodal pattern, with peaks at 16:00 and 07:00. (4) Short-duration events occur under the background of a weaker and eastward-displaced Western Pacific Subtropical High (WPSH), with an abnormal cyclonic circulation extending from central Hunan to the southeastern coast of China. In contrast, medium-duration and long-duration events occur under a westward-extended and stronger WPSH, accompanied by an anomalous anticyclone over the South China Sea to South China, which enhances moisture transport from the Bay of Bengal and the South China Sea to central Hunan, These findings provide scientific references for monitoring, early warning, and disaster risk mitigation of extreme precipitation events in central Human.

关键词

极端降水事件 / 时空分布 / 异常环流 / 湘中地区

Key words

extreme precipitation events / spatial and temporal distribution / anomalous circulation / central Hunan

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基金资助

湖南省联合基金重点项目(2026JJ30038)

中国气象局创新发展专项(CXFZ2026J014)

湖南省气象局创新发展专项(CXFZ2024-FZZX16，CXFZ2025-MSXM07)