基于SPEI的甘南高原气象干旱变化特征

Meteorological drought variation characteristics in the Gannan Plateau based on standardized precipitation evapotranspiration index

干旱灾害是甘南高原发生最频繁的气象灾害之一,严重影响该地区农牧业生产和生态环境安全。利用1973—2022年甘南高原及周边31个气象观测站逐月降水和气温观测数据,选取标准化降水蒸散指数(Standardized Precipitation Evapotranspiration Index,SPEI)表征气象干旱,采用Mann-Kendall检验和Sen’s slope估计方法,研究甘南高原年、季尺度的干旱时空分布及变化特征。结果表明:近50 a来,甘南高原年SPEI呈显著减小趋势,全域整体趋向干旱化,1986年为突变年。干旱变化趋势存在季节差异,夏、秋季呈干旱加剧趋势,春、冬季则相反。年和季SPEI变化趋势存在空间差异性,年和秋季全域呈干旱化趋势;夏季甘南高原中东部呈干旱加剧趋势,春季与夏季相似,但春季干旱加重区域和干旱化程度明显小于夏季;冬季整体呈干旱减轻趋势。甘南高原年和季节尺度不同等级干旱发生频率有明显的空间差异,高原中东部轻旱频发,高原南部中旱和重旱高发,特旱各区域发生频率均较低;高原西部干旱发生频率总体小于高原中东部。

Drought disaster is one of the most frequent meteorological disasters in the Gannan Plateau,which seriously affects agricul-tural and animal husbandry production and ecological environment security in this region.Monthly precipitation and air temperature data from 31 meteorological stations in the Gannan Plateau and its surrounding areas from 1973 to 2022 are used to characterize meteo-rological drought employing the Standardized Precipitation Evapotranspiration Index(SPEI),and the temporal and spatial distribution of drought and its variations on annual and seasonal scales in the Gannan Plateau are analyzed by using Mann-Kendall test and Sen’s slope estimation methods.Results show that the annual SPEI in the Gannan Plateau presented significant downward trend with an obvi-ous turning point in 1986,and the whole Gannan Plateau tended to be dry in the past 50 years.There were seasonal differences in the variation trend of drought,and the trend of drought intensified in summer and autumn,but in spring and winter it mitigated.In addition,there were spatial differences in the trend of annual and seasonal SPEI.In summer,it presented drought intensification trend in the middle and eastern regions of the Gannan Plateau,and in spring it showed similar to that in summer,but the area and degree of drought intensification were obviously smaller than that in summer.While in winter,it showed drought decreasing trend in the whole region.There were obvious spatial differences in the frequency of drought with different levels in the Gannan Plateau at the annual and sea-sonal scales.Light drought occurred frequently in the central and eastern parts of the Gannan Plateau,while medium and severe drought occurred frequently in the southern part of the Gannan Plateau,and the frequency of serious drought was less across the whole regions.Overall,the frequency of drought in the western was less than that in the central and eastern parts of the Gannan Plateau.