1901~2020年中国西北地区干湿变化的时空特征

Spatiotemporal characteristics of dry and wet changes in Northwest China over 1901~2020

西北地区是我国西部大开发的主战场和重要的生态安全屏障,研究西北地区在全球变化背景下的干湿演化规律对我国高质量发展具有重要意义。本研究选取0.5°空间分辨率的逐月标准化降水蒸散指数(SPEI)格点数据集,利用Mann-Kendall趋势检验、EOF经验正交函数分解以及小波分析等方法,探索西北地区1901~2020年月尺度、年尺度、4年尺度的干湿变化时空演化特征。研究结果表明,西北地区SPEI值总体上呈逐渐下降的趋势。空间变化上,西北地区干湿变化情况存在明显的空间分异,研究区西南和西北部分表现为湿润趋势,而在中部和东部则表现为干旱趋势,这种反相变化特征在长时间尺度干旱上表现更加明显。时空模态的分解表明,西北地区月尺度干湿演化具有空间一致性,而在较长时间尺度上,区域干湿演化跷跷板模式占据主导地位,且这种空间差异模式在1990年代末期明显增强。在时间变化上,西北地区干旱具有较显著的2~8年短时间尺度的周期性变化规律,同时具有明显且连续的约11年和约22年长时间尺度的周期性变化特征。基于本分析结果,可以推断西北地区干湿变化时空演化特征可能受太阳活动和厄尔尼诺与南方涛动(ENSO)等因素的影响。研究结果还表明,SPEI指数在中国西北地区干旱分析研究中具有较好的适用性,研究结果可为该地区预防干旱事件和适应气候变化工作提供参考。

The elucidation of dry and wet change patterns in Northwest China is of great significance for advancing regional economic development.However,there is currently ongoing debate regarding the temporal evolution,spatial pattern,and driving mechanisms of the drought conditions in this region.In this study,we investigate spatiotemporal variations of drought in Northwest China over 1901~2020 based on the standardized precipitation evapotranspiration index(SPEI)at multi scales of 1,12,and 48 months.The trend significance and magnitude of SPEI in multi-timescale were analyzed using the Mann-Kendall trend test.The empirical orthogonal function(EOF)and wavelet analysis were applied to analyze the spatial patterns and periods in SPEI series.The results showed that the spatial disparities in the evolution of drought in the Northwest Region become more pronounced as the timescale increased.An overall drought trend was detected in most regions of Northwest China,except the belt from northwestern and southwestern of study region.The decomposition of spatial-temporal modes reveals that the evolution of drought conditions on 1-month scale exhibits spatial consistency.Meanwhile,a seesaw pattern prevails over longer time scales,with this spatially differentiated pattern significantly intensifying towards the 1990s.Drought in the study region exhibits a pronounced period of 2~8 years,alongside a sustained cyclic pattern on a longer time scale of approximately 11 and 22 years.Based on the results of this analysis,it can be inferred that the spatial and temporal evolution characteristics of dry and wet changes in the Northwest China may be influenced by solar activity and El Niño and Southern Oscillation(ENSO).The results of this study also show that the SPEI index has good applicability in drought analysis and research in Northwest China,and the results can be used as a reference for preventing drought events and adapting to climate change in the region.