Abstract:

Clarifying the spatial-temporal differentiation of drought in the Hexi Corridor and its surrounding regions can provide a scientific support basis for regional drought prevention and disaster reduction, sustainable management of oasis agriculture, and the maintenance of ecological security barriers. In this study, the Hexi Corridor and its surrounding areas were divided into three sub-regions: the northwestern Hexi region, the eastern Hexi region, and the Qilian Mountains. Monthly observation data from 17 meteorological stations during 1961-2020 were used. The Standardized Precipitation-Evapotranspiration Index (SPEI) was adopted as the drought indicator. Methods including the Mann-Kendall mutation test, run-length theory and spatial interpolation were employed to analyze regional climate fluctuation characteristics and the spatial-temporal evolution of drought. The results show that: (1) The climate of the Hexi Corridor and its surrounding areas generally exhibits an overall warming-wetting trend. The warming rates decrease in the order of the eastern Hexi region, the Qilian Mountains and the northwestern Hexi region, with values of 0.42, 0.38 and 0.32 ℃·(10 a)^-1, respectively. Precipitation in the Qilian Mountains increases significantly at a rate of 9.1 mm·(10 a)^-1 (p<0.05), whereas only slight increasing trends are observed in the other regions. (2) Multi-timescale drought analysis indicates that drought in the northwestern Hexi Corridor is characterized by a short-term response, whereas the Qilian Mountains and the eastern Hexi Corridor exhibit a cumulative response. Drought intensity across the study area exhibits an evolutionary feature of “the widespread occurrence of mild drought, the expansion of moderate drought, and the emergence of extreme drought”. Since the beginning of the 21st century, the frequencies of moderate and extreme drought events have increased markedly. (3) Significant spatial differences are observed among drought severity levels. The northwestern Hexi Corridor is dominated by mild drought over the long term,with relatively stable drought condition. The occurrence frequencies of severe and extreme drought increase obviously in the eastern Hexi Corridor and the Qilian Mountains. Drought characteristics in the Qilian Mountains shift from increasing occurrence frequency to intensifying severity, posing a growing threat to the regional water conservation function.

Key words: Hexi Corridor, drought evolution, SPEI, warming-wetting, the Qilian Mountains

摘要：

厘清河西走廊及周边区域干旱时空分异规律，可为区域防旱减灾、绿洲农业可持续管理与稳固生态屏障提供科学依据。将河西走廊及周边区域划分为河西西北部、河西东部及祁连山区3个子区域，利用1961—2020年17个气象站点逐月观测资料，以标准化降水蒸散指数（Standardized Precipitation Evapotranspiration Index，SPEI）为干旱指标，采用Mann-Kendall突变检验、游程理论及空间插值等方法，分析研究区气候波动特征与干旱时空演变规律。结果表明：（1）河西走廊及周边区域气候总体呈暖湿化趋势，增温速率由高至低依次为河西东部、祁连山区、河西西北部，增温速率分别为0.42、0.38、0.32 ℃·（10 a）^-1；祁连山区降水量以9.1 mm·（10 a）^-1速率显著增多（p<0.05），其余地区降水仅呈微弱上升趋势。（2）多时间尺度干旱过程分析显示：河西西北部干旱为短期响应型，祁连山区与河西东部为累积响应型；研究区干旱强度呈“轻旱普及、中旱扩张、特旱显现”的演变特征，21世纪以来中旱、特旱发生频次显著上升。（3）干旱等级空间分异显著：河西西北部长期以轻旱为主，干旱态势相对稳定；河西东部与祁连山区重旱、特旱发生频率明显增多；祁连山区干旱特征由频次增多转向强度增强，水源涵养功能遭受威胁。

关键词: 河西走廊, 干旱演变, SPEI, 暖湿化, 祁连山区