湖北省夏季季内旱涝变化及成因分析

    Association and causes of intra-seasonal droughts and floods variations during summer in Hubei Province

    • 摘要: 受气候变化和人为活动等因素叠加影响,湖北省夏季持续性旱涝、转折性旱涝频发。为了厘清两者的相对贡献及其演变特征,基于逐日降水资料、NCEP/NCAR再分析资料,利用经验正交函数分解方法、回归分析等统计方法,探讨了湖北省夏季季内旱涝变化的主要模态及成因。结果表明:(1)湖北省夏季季内旱涝变化主要有两个模态,表现为持续性旱涝模态和转折性旱涝模态。前者解释方差占比高于后者。(2)不同的旱涝变化模态对应着不同的环流演变特征。持续性旱涝年,稳定维持的东亚—太平洋遥相关波列起到重要作用,初夏还伴随着“丝绸之路”遥相关波列。转折性旱涝年,环流调整明显,欧亚大陆上空环流由初夏半圆波列调整为盛夏类欧亚型波列。(3)进一步研究发现,影响持续性、转折性旱涝的海温关键区时空差异明显。赤道中东太平洋、热带印度洋、北大西洋等季节尺度海温异常可以造成东亚—太平洋和“丝绸之路”遥相关波列的产生及维持,湖北省夏季易发生持续性旱涝;北大西洋三极子月尺度海温异常,通过激发欧亚中高纬波列,利于湖北省夏季出现转折性旱涝。研究成果可为长江中游地区次季节气候预测、水资源精细化管理提供科学支撑与决策参考。

       

      Abstract: Under the combined influence of climate change and anthropogenic activities, persistent and transitional drought-flood events have become increasingly frequent during summer in Hubei Province. To clarify the relative contributions and their evolutionary characteristics, this study investigates the dominant modes and causes of intraseasonal summer drought-flood variability in Hubei, using daily precipitation data and NCEP/NCAR reanalysis datasets, along with statistical methods such as Empirical Orthogonal Function decomposition and regression analysis. The results show that: (1) The intra-seasonal drought and flood variations in Hubei summer are primarily characterized by two modes: a persistent drought-flood mode and a transitional drought-flood mode. The former accounts for a higher proportion of explained variance than the latter. (2) Different drought-flood modes correspond to distinct atmospheric circulation evolution characteristics. In persistent drought-flood years, a stable East Asia-Pacific teleconnection wave train plays a crucial role, accompanied by the ‘Silk Road’ teleconnection wave train in early summer. In transitional drought-flood years, the circulation undergoes significant adjustments, shifting from a semicircular wave train over Eurasia in early summer to a Eurasian-like wave train in mid-summer. (3) Further research reveals notable spatio-temporal differences in the key sea surface temperature regions influencing persistent and transitional drought-flood events. Seasonal-scale SST anomalies in the equatorial central-eastern Pacific, tropical Indian Ocean, and North Atlantic can induce the formation and maintenance of the EAP and ‘Silk Road’ teleconnection wave trains, making Hubei prone to persistent drought-flood conditions in summer. In contrast, monthly-scale SST anomalies associated with the North Atlantic tripole can excite different Eurasian mid-high latitude wave trains, thereby favoring transitional drought-flood occurrences in Hubei during summer. The research findings can provide scientific support and decision-making references for subseasonal climate prediction and refined water resource management in the middle reaches of the Yangtze River region.

       

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