西南地区1902—2018年干旱时空演变特征分析

鉴于西南地区干旱的危害程度及其严峻形势,定量刻画干旱时空特征、揭示干旱发展规律,已成为抗旱防灾、保障农业健康发展的迫切要求。基于1902—2018年标准化降水蒸散指数(SPEI)数据,统计了西南地区不同等级干旱发生频率及干旱强度,并采用Sen趋势分析、Mann-Kendall检验法和经验正交函数(EOF)分析方法研究了西南地区干旱的时空演变特征,以期为西南地区干旱变化及生态维护提供科学依据。结果表明:(1)1902—2018年西南地区SPEI12整体呈下降趋势,下降速率为0.025/10 a,其中1954—1974年呈干旱—湿润的频繁交替,发生多次不显著突变;(2)西南地区干旱强度均呈增强趋势,其中中旱和重旱强度增强趋势显著;(3)西南地区干旱发生频率存在空间分布差异,其中轻旱发生频率最高,极端干旱最低;(4)西南地区干旱变化趋势以不显著下降为主,占研究区面积的68.22%,表明西南地区百年来呈干旱化趋势;(5)干旱时空模态分析中,3种模态分别反映了研究区干旱全区相同、南北相反、东西相反的分布特征。综上所述,揭示了西南地区干旱的时空变化基本特征。

Spatiotemporal Evolution Characteristics of Meteorological Drought in Southwest China from 1902 to 2018

In view of the severity of drought in southwest China, it has become an urgent requirement to quantitatively characterize the spatio-temporal evolution of drought and reveal the law of drought development. Based on standardized precipitation evapotranspiration index(SPEI)data from 1902 to 2018, we counted the frequency and intensity of droughts of different grades in the southwestern region. Sen trend analysis, Mann-Kendall test and empirical orthogonal function analysis methods were used to study the temporal and spatial evolution characteristics of drought in southwest China in order to provide a scientific basis for drought changes and ecological maintenance in southwest China. The results show that:(1)the annual SPEI in southwest China from 1902 to 2018 showed a downward trend at a rate of 0.025/decade, among wich there was a frequent drought-humidity alternation from 1954 to 1974, with multiple insignificant mutations;(2)the drought intensity in the southwestern region showed an increasing trend, among which the intensity of moderate drought and severe drought increased significantly;(3)the frequency of drought in southwestern region was different in spatial distribution, among which the frequency of light drought was the highest and the extreme drought was the lowest; the change trend was mainly insignificant decline, accounting for 68.22%, indicating an aridity trend in the southwest region over the past century;(5)in the analysis of drought spatiotemporal modalities, the three modes reflected the same, south-north and east-west distribution characteristics of drought in the study area, respectively. In summary, spatiotemporal evolution characteristics of meteorological drought in the southwest are revealed.