| 摘要: |
| 气象干旱是影响人类社会最严重的气象灾害之一，且对中纬度干旱半干旱地区的危害更为显著。为探究气候变化背景下我国甘肃地区干旱事件的时空分布，首先根据甘肃1969—2018年月值气象资料计算标准化降水蒸散指数（SPEI），通过游程理论提取干旱事件。随后采用REOF旋转正交分解将研究区划分成5个气候子区，并以每个子区为单位，基于B-G分割算法细致对比各子区不同时间尺度干旱事件的变化特征和演变趋势。最后，采用相关性分析探究各子区干旱事件的驱动因素。主要结论有：（1）研究区干旱累积历时呈微弱增加趋势（0.475 d·(10a)−1）并存在19 a的主周期，干旱强度呈先缓和再加剧趋势，尤其是2000年后干旱加剧显著，并呈现出西北部干旱减轻、东南部干旱加剧的空间变化趋势。（2）REOF分解的前五个模态累积贡献率为53.06%，主要的空间分布模态为：全区一致型模态和南北反向分异模态。将研究区分为5个干旱子区：河西地区、河东中部地区、河东东部地区、乌鞘岭地区和河东西部地区。（3）河西地区自1988年以来气象干旱显著缓和（P＜0.01）；河东东、中、西部地区存在不同程度的干旱加剧趋势（0.120·(10a)−1、0.129·(10a)−1、0.072·(10a)−1，P＞0.05）；乌鞘岭地区在1975年以后气象干旱显著缓和（P＜0.01），形成了干旱缓和与加剧变化的分水岭区域。（4）季节上，河西地区仅夏季呈缓和趋势；河东东部地区春季呈显著干旱化趋势，而秋季相反；河东西部地区春夏两季气候干旱化趋势明显而秋冬两季相反；河东中部地区和乌鞘岭地区季节变化呈明显一致性，前者四季均呈干旱化趋势，且春季干旱化最剧烈，后者四季均呈缓和趋势，且冬季最明显。（5）研究区气象干旱受当地气候因子和环流因子因素的共同影响，河西地区和河东西部地区对气温的响应明显而河东中、东部地区则对降水量的响应明显；乌鞘岭地区对日照时数的响应明显；NAO指数对研究区夏季气象干旱存在重要影响而ENSO事件（厄尔尼诺-南方涛动）对研究区春秋两季（尤其是春季）气象干旱存在重要影响。 |
| 关键词: 甘肃 SPEI REOF 干旱事件 时空变化 |
| DOI：10.7515/JEE222067 |
| CSTR：32259.14.JEE222067 |
| 分类号: |
| 基金项目: |
| 英文基金项目: |
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| Analysis of the spatial and temporal variation of the meteorological drought in Gansu Province in recent 50 years |
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TIAN Hanwen, ZHAO Yan, CHEN Yiping, ZHANG Yi
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1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
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| Abstract: |
| Background, aim, and scope The escalating impacts of global warming have precipitated a notable upswing in drought occurrences, yielding far-reaching repercussions across ecological systems, agricultural productivity, societal dynamics, and beyond. The Gansu region epitomizes an arid climatic setting, where a confluence of natural and anthropogenic factors has rendered the intrinsic recuperative capacity of its environment frail in the face of drought events. In the context of climate change, an investigation into the temporal and spatial dynamics of drought incidents within this research domain holds the potential to illuminate broader patterns in climate transition across northwestern China and to decipher how arid regions are responding to the ramifications of global climate shifts. Materials and methods Leveraging the SPEI index algorithm in tandem with nearly half a century’s worth of meteorological data encompassing Gansu Province, we employed the course theory to extract instances of drought events based on the drought index. Subsequently, the application of REOF rotation facilitated the subdivision of arid sub-regions. Results The findings underscore a prolonged trajectory in the duration of drought events within the examination area, exhibiting a rate of extension at 0.475 d·(10a)−1. Notably, this duration displayed an initial stretch, succeeded by a contraction, followed by a gradual resurgence commencing in the mid-1990s. A prevailing cycle of approximately was evident across the entire temporal scope. While the Wushaoling and Jiuquan areas at the western terminus of the Hexi Corridor proved exceptions, manifesting distinct drought duration patterns, the broader trend indicated an incremental elongation of drought duration across the remaining areas. Discussion (1) Gansu’s character as an arid agricultural zone. Gansu stands as a quintessential representation of a dry farming region. Within this context, meteorological drought stands out as a pivotal natural factor, triggering agricultural calamities with significant ramifications for both local livelihoods and agricultural output. Against the backdrop of the overarching temperature escalation in northwestern China, water availability has emerged as the predominant determinant dictating the area’s aridity and moisture conditions. (2) Drought disaster’s impacts and escalation. Drought disasters, assuming the role of a primary natural catastrophe, wield substantial influence over agricultural productivity and the developmental progress of ecological civilization within northwestern China. The escalation in both the frequency and intensity of drought events has exacerbated the toll exacted by these occurrences. (3) Ecological vulnerability and recent shifts. The eastern segment of the study area, particularly the Longdong Loess Plateau, holds pivotal significance within the broader Loess Plateau context. Predominantly reliant on rain-fed agriculture, this region is characterized by an ecologically fragile environment, grappling with severe soil erosion and water loss. In recent years, a noteworthy upswing in springtime drought events has yielded multifaceted impacts. These ramifications encompass not only the agricultural and ecological spheres of the Longdong Loess Plateau, but also extend to the production and processing of distinctive agricultural commodities, rural poverty alleviation efforts, and overall agricultural sustainability. This has engendered a palpable effect on the region’s trajectory toward stable and sustainable agricultural development. Conclusions The study spotlights a mounting trajectory in drought intensity within the examined area, with meteorological drought, particularly after 2000, exhibiting a spatial shift toward ameliorated drought conditions in the northwest, juxtaposed with a deteriorating scenario in the southeast. Notable easing of summer droughts is evident in the Hexi region, while the remaining three seasons exhibit a subdued drought tendency. Within eastern Hedong, spring displays a significant drought trend, albeit contrasted by a mitigation of autumnal drought. Spring and summer drought intensification emerges both in the eastern and western sectors of Hedong, marked by abrupt shifts in 2002 and 2000, respectively. Local climatic elements and atmospheric circulation patterns distinctly influence the meteorological drought in the study area. Temperature influences resonate prominently in the Hexi and western Hedong zones, while precipitation effects manifest in the middle and eastern Hedong regions. Sunshine duration significantly impacts the Wushaoling area. Furthermore, the NAO index exerts a pronounced impact on summer meteorological droughts, while the ENSO events wield substantial influence during spring and autumn, particularly the former. Recommendations and perspectives In light of the pronounced warm and humid climatic conditions prevalent across the central and western reaches of the research domain, it remains imperative to maintain vigilance regarding variances in seasonal moisture patterns. Particularly noteworthy is the escalating intensity of springtime drought in select areas. This emerging trend holds significant implications for rain-fed agriculture within the region, posing challenges to optimizing surface water allocation and impeding the sustainable evolution of the natural environment. |
| Key words: Gansu SPEI REOF drought events temporal and spatial variation |
