1961-2020年黄河流域干燥度时空变化及其对植被NDVI的影响

Spatiotemporal variations in aridity and its impact on vegetation NDVI in the Yellow River Basin from 1961 to 2020

基于黄河流域224个气象站点1961—2020年气象数据和2000—2020年MODIS的归一化植被指数(NDVI)数据,分析干燥度时空分布规律及其对NDVI的影响。结果表明:1961—2020年黄河流域年平均干燥度气候倾向率为-0.03·(10 a)^(-1),其多年平均值为2.56;从各站变化的区域分布看,黄河流域北部站点变化以下降为主(52.2%),中部以南站点以上升为主(41.5%)。在空间上,黄河流域干燥度总体呈西北高、东南低,表现为上游(3.74)>中游(1.99)>下游(1.74),上游地区包含干旱亚区、半干旱亚区和半湿润亚区,中游和下游地区大多为半湿润亚区。逐步回归分析显示,干燥度主要受降水量的影响,大部分地区年均干燥度减少是由太阳总辐射减少、降水量增加和气温降低造成的。2000—2020年黄河流域NDVI平均值为0.30,在空间上整体呈东南高、西北低,上游较小、下游最高;与干燥度呈极显著负相关(r=-0.52,P<0.01,n=224),特别是在上中游地区。

Based on the meteorological data of 224 stations in the Yellow River Basin from 1961 to 2020 and the MODIS NDVI vegetation data from 2000 to 2020,the spatiotemporal distribution patterns of aridity were analyzed,as well as its impacts on the vegetation NDVI.Results show that the tendency rate of annual averaged aridity in the Yellow River Basin is-0.03 per decade from 1961 to 2020,with a multi-year average value of 2.56.In terms of the regional variability,the northern stations are mainly characterized by a decreasing trend(52.2%),while the central and southern stations primarily exhibit an increasing trend(41.5%).As for the aridity spatial distributions,it generally decreases from northwest to southeast,with the highest values in the upper reaches(3.74),followed by the middle reaches(1.99)and lower reaches(1.74).The upper reaches include arid,semi-arid,and semi-humid subregions,while the middle and lower reaches are mostly semi-humid subregions.Stepwise regression analysis indicates that aridity is primarily impacted by the local precipitation.The reduction in annual average aridity in most areas could be attributed to decreased total solar radiation,increased precipitation,and lower temperatures.The averaged NDVI is 0.30 in the Yellow River Basin from 2000 to 2020,with a distribution of higher values in the southeast(lower reaches)and lower values in the northwest(upper reaches).The NDVI is a significantly negative correlation with the aridity(r=-0.52,P<0.01,n=224),especially in upper and middle reaches of the Yellow River Basin.