基于SPEI的黄河流域多尺度干湿特征分析

Analysis of multi-scalar characteristics of dry and wet conditions in the Yellow River Basin based on SPEI

基于1960-2020年黄河流域70个气象站点逐日观测资料,利用降水量和潜在蒸散发计算标准化降水蒸散指数(Standardized Precipitation Evapotranspiration Index,SPEI),研究了1960-2020年黄河流域干湿演变及持续性特征,分析了气象因子对流域干湿变化的影响。结果表明:(1)不同时间尺度上,SPEI反映的干湿等级及频率有一定的差异性,干湿等级以正常和轻度为主;年际变化上,1960-2020年黄河流域夏季呈不显著变湿趋势,流域年、春季、秋季和冬季均呈不显著的变干趋势。空间尺度上,夏季以变湿为主,SPEI呈上升趋势的站点占总站点的比例为64.29%;流域年、春季、秋季和冬季以变干为主,SPEI呈下降趋势的站点占总站点的比例分别为51.43%、62.86%、64.29%和51.43%。(2)从干湿事件的不同时间尺度看,1970-1979年为典型的偏干时段,而1960-1969年为典型的偏湿时段,干湿事件发生频率为:秋季>夏季>春季>冬季。(3)从干湿事件的持续性特征看,持续性干旱事件强度变大,主要发生在秋季和冬季;持续性湿润事件强度增加,主要发生在秋季。(4)1960-2020年黄河流域年SPEI呈下降趋势,主要是由降水量、平均风速及相对湿度的降低共同作用的。

Based on daily data from 70 meteorological stations in the Yellow River Basin from 1960 to 2020,the Standardized Precipitation Evapotranspiration Index(SPEI)based on precipitation and potential evapotranspiration was calculated.Then,the evolution and persistence characteristics of dry-wet change of the Yellow River Basin from 1960 to 2020 were studied and their influence on meteorological factors was analyzed.Results showed the following:(1)There were differences in dry and wet grades and frequencies among the SPEI at different time scales and dry and wet levels were dominated by normal and light conditions.There was an insignificant wetness trend in summer and an insignificant dryness trend annually,and during spring,autumn,and winter from 1960 to 2020 in the Yellow River Basin.Geographically,the summer climate was mainly wet and 64.29%of meteorological stations showed an increased SPEI.The annual,spring,autumn,and winter climate in the Yellow River Basin was mainly dry and 51.43%,62.86%,64.29%,and 51.43%of meteorological stations showed a decrease SPEI,respectively.(2)For the different time scales of dry and wet events,1970-1979 was a partial dry period,whereas 1960-1969 was a partial wet period,and the frequency of dry and wet events was as follows:autumn>summer>spring>winter.(3)From persistent characteristics of dry and wet events,the intensity of ongoing drought events increased and occurred mainly in autumn and winter,whereas the intensity of persistent wet events increased and occurred mainly in autumn.(4)A decreasing trend in the SPEI from 1960 to 2020 was mainly due to combined effects of a decrease of precipitation,average wind speed and relative humidity.