Hunan is a region prone to drought disasters. Conducting an analysis of the characteristics and causes of drought events is of great practical significance for improving the monitoring and prediction level of drought disasters in Hunan and reducing disaster losses. Based on daily precipitation data from ground observation stations and reanalysis data, the characteristics and causes of persistent extreme drought events that occurred in Hunan in the summer, autumn and winter of 2022/2023 are analyzed. The results indicate that the continuous drought in the summer, autumn and winter of 2022/2023 in Hunan has the characteristics of significantly less precipitation (The average accumulated precipitation in the whole province was the least in the same period since 1961) and a long duration (201 days). And in the summer of 2022, there was also a rare extremely high temperature heatwave throughout the entire Yangtze River basin, with multiple indicators such as average temperature and high temperature days in Hunan reaching historical extremes since 1961, which had a serious impact on industrial and agricultural production and people’s lives in Hunan. The ongoing drought event in summer, autumn and winter is closely related to sea surface temperature and circulation anomalies. In the early spring, the La Niña event and the negative phase mode of the Indian Ocean dipole led to the enhancement of the Walker circulation, and the west Pacific subtropical high (referred to as the “WPSH”) strengthened and extended westward and uplifted northward. From August to November 2022, the WPSH extended westward to 105°E, and the Hunan region was controlled by it, the prevailing downdraft led to the development of drought in summer and autumn in Hunan. From December 2022 to early February 2023, the WPSH was weaker compared to the same period in previous years, and the East Asian trough was strengthened and its location was east of Hunan, making it difficult to guide cold air southward to affect Hunan. The Indian-Myanmar trough was weaker, which was not conducive to the development of southwest airflow in front of the trough. The water vapor transport over Hunan region was hindered, leading to sustained drought in winter in Hunan.

persistent drought in summer, autumn and winter, Hunan, drought causes, atmospheric circulation

湖南是干旱灾害多发区，针对湖南地区开展干旱事件特征与成因分析，对于提高湖南干旱灾害的监测预测水平、减少灾害损失具有重要现实意义。基于地面观测站日降水数据和再分析资料，分析 2022/2023年夏秋冬季湖南发生的持续极端干旱事件特征和成因。结果表明，这次湖南夏、秋、冬三季连旱具有降水显著偏少（全省平均累积降水量为 1961年以来历史同期最少）、持续时间长（历时 201 d）的特点，同时 2022年夏季还伴随罕见的长江全流域性极端高温热浪，湖南平均气温、高温天数等多项指标均达到 1961年以来历史同期极值，给湖南工农业生产和人民生活带来严重影响。本次夏秋冬持续干旱事件与海温和环流异常密切相关，前期春季拉尼娜事件和印度洋偶极子负位相模态导致沃克环流增强，西太平洋副热带高压（简称“西太副高”）加强西伸和北抬。2022 年 8—11 月西太副高西伸至 105°E，湖南地区受其控制，盛行下沉气流，导致湖南夏秋干旱发展；12 月至2023 年 2 月上旬，西太副高相比历年同期偏弱，东亚大槽增强，且位置在湖南以东，难以引导冷空气南下影响湖南，印缅槽偏弱，不利于槽前西南气流发展，湖南地区水汽输送受阻，导致冬季湖南干旱持续。

夏秋冬三季连旱, 湖南, 干旱成因, 大气环流