洞庭湖流域复合高温干旱事件的时空演变特征

Spatiotemporal evolution characteristics of compound drought and heatwave events in Dongting Lake Basin

摘要

【目的】全球气候变暖背景下，洞庭湖流域极端天气频发，复合高温干旱事件对社会经济和生态环境影响加剧。分析洞庭湖流域复合高温干旱的时空演变规律及其对大气环流因子的响应，对于区域防灾减灾具有重要意义。【方法】基于1971—2020年洞庭湖流域日最高气温、标准化降水蒸散发指数(SPEI)与大气环流指数，利用趋势分析法和小波相干分析等方法，分析该流域复合高温干旱事件的时空演变规律及大气环流驱动机制。【结果】结果表明：1971—2020年洞庭湖流域年日最高温呈显著上升趋势，增幅达0.28℃/10 a。SPEI年际波动大，无明显规律，1983—1988年、2003—2009年干旱相对频繁且持续；流域复合高温干旱事件发生日数和持续时间呈增加趋势，分别以2.2 d/10 a、1.3 d/10 a和0.3 d/10 a以及0.9 d/10 a、0.6 d/10 a和0.2 d/10 a速率上升，年代际变化特征显著；从季节性分布来看，复合事件主要发生在7月和8月；后25 a,复合事件发生天数和持续时间相较于前25 a有所增加；空间频率变化上呈“东增西减”分异，东北部增幅最大，达200%以上；复合事件频次受多尺度大气环流因子协同影响，其中厄尔尼诺-南方涛动(ENSO)、太平洋年代际振荡(PDO)、北大西洋涛动(NAO)及西太平洋副热带高压(WPSH)作用较为显著。【结论】1971—2020年，洞庭湖流域复合高温干旱事件发生天数和持续时间呈增加趋势，空间分布差异显著，东部总体呈增加趋势，减少的区域主要分布在西部；ENSO、PDO、NAO等大气环流因子是影响流域复合高温干旱事件发生的重要影响因素。研究结果为区域复合灾害风险评估与适应性管理提供了科学依据。

Abstract

[Objective] In the context of global climate warming, extreme weather events occur with increasing frequency in the Dongting Lake Basin, and compound drought and heatwave events(CDHEs) exacerbate their influence on socioeconomy and the ecological environment. Analyzing the spatiotemporal evolution patterns of the CDHEs in the Dongting Lake Basin and their response to atmospheric circulation factors is of great significance for regional disaster prevention and mitigation. [Methods] Based on daily maximum temperatures, Standardized Precipitation Evapotranspiration Index(SPEI), and atmospheric circulation indices from 1971 to 2020, trend analysis and wavelet coherence analysis were employed to analyze the spatiotemporal evolution patterns and atmospheric circulation driving mechanisms of CDHEs in the Dongting Lake Basin. [Results] The results showed that from 1971 to 2020, the annual maximum daily temperature in the Dongting Lake Basin showed a significant increasing trend, with a rate of 0.28 ℃/10 a. The SPEI showed substantial interannual fluctuations, with no clear pattern. Droughts were relatively frequent and persistent, occurring during 1983—1988 and 2003—2009. The number of days and duration of CDHEs in the river basin demonstrated increasing trends, with the number of days increasing at rates of 2.2 d/10 a, 1.3 d/10 a, 0.3 d/10 a, and the duration increasing at 0.9 d/10 a, 0.6 d/10 a, 0.2 d/10 a, respectively, exhibiting significant interdecadal variation characteristics. Seasonally, CDHEs mainly occurred in July and August. In the latter 25 years, the number of days and duration of these events increased compared to the former 25 years. Spatial frequency variations exhibited an “increase in the east and decrease in the west” pattern. The northeastern region showed the most significant increase, exceeding 200%. The frequency of CDHEs was influenced by multi-scale atmospheric circulation factors, among which the El Ni1o-Southern Oscillation(ENSO), Pacific Decadal Oscillation(PDO), North Atlantic Oscillation(NAO), and Western Pacific Subtropical High(WPSH) demonstrated more significant influence. [Conclusion] From 1971 to 2020, the number of days and duration of CDHEs in the Dongting Lake Basin showed increasing trends, with significant spatial distribution differences. An overall increasing trend was observed in the east, while the decreasing areas were mainly located in the west. Atmospheric circulation factors such as ENSO, PDO, and NAO were important influencing factors of the occurrence of CDHEs. These findings provide a scientific basis for regional compound disaster risk assessment and adaptive management.

关键词

洞庭湖流域 / 复合高温干旱事件 / 日尺度SPEI / 时空变化 / 大气环流因子 / 小波相干分析 / 极端高温 / 影响因素

Key words

Dongting Lake Basin / compound drought and heatwave events / daily-scale SPEI / spatiotemporal variation / atmospheric circulation factors / wavelet coherence analysis / extreme high temperature / influencing factor

基金资助

国家自然科学基金项目(42471038)

福建省自然科学基金项目(2023J01285)