近20年黄土高原干旱变化特征及其影响因素

Variation Characteristics and Influencing Factors of Drought in the Loess Plateau in Recent 20 Years

为促进黄土高原农业和生态环境可持续发展,基于2001—2020年MODIS蒸散产品和气象站点数据,利用作物缺水指数(crop water stress index,CWSI)、Theil-Sen Median趋势分析、Mann-Kendall检验和偏相关分析等方法,探讨了黄土高原干旱变化特征及其影响因素。结果表明:①年际上,2001—2020年黄土高原CWSI呈显著线性下降过程,下降速率为0.0058 a^(-1)(P<0.01)。干旱程度呈先减(2001—2018年)后增(2018—2020年)过程;②空间上,CWSI以减少趋势为主,显著减少趋势占区域总面积91.24%,其中青海、甘肃、宁夏、陕西南部地区CWSI下降速率较快;③黄土高原CWSI与气温以负偏相关关系为主,显著负偏相关占区域面积的7.78%,集中分布于青海东部、山西南部和河南北部;与降水以负偏相关关系为主,显著负偏相关占区域总面积60.88%,集中分布于黄土高原西南部和东部地区。气温升高背景下,降水增加促使黄土高原实际蒸发显著增加、潜在蒸发不显著减少,导致CWSI显著下降。研究结论认为降水是黄土高原CWSI下降的主要影响因素,年降水量增加减缓了黄土高原干旱趋势。

In order to promote the sustainable development of agriculture and ecological environment in the Loess Plateau,based on MODIS evapotranspiration products and meteorological station data from 2001 to 2020,the characteristics of drought change and its influencing factors in the Loess Plateau were discussed by using crop water stress index(CWSI),Theil-Sen Median trend analysis,Mann-Kendall test and partial correlation analysis.The results show these as follows.Interannually,the CWSI of the Loess Plateau showed a significant linear decline process from 2001 to 2020,and the decline rate was 0.0058·a^(-1)(P<0.01).The degree of drought decreased first(2001—2018)and then increased(2018—2020).Spatially,the CWSI was dominated by a decreasing trend,with a significant decreasing trend accounting for 91.24%of the total area of the region.Among them,the CWSI in Qinghai,Gansu,Ningxia and southern Shaanxi decreased faster.The negative partial correlation between CWSI and temperature was dominant in the Loess Plateau,and the significant negative partial correlation accounted for 7.78%of the regional area,which was concentrated in the eastern Qinghai,southern ShanXi'and northern Henan.There is a negative partial correlation with precipitation,which accounts for 60.88%of the total area and is concentrated in the southwest and east of the Loess Plateau.Under the background of rising temperature,the increase of precipitation promoted the significant increase of ET(evapotranspiration)and insignificant decrease of PET(potential evapotranspiration)in the Loess Plateau,resulting in a significant decrease of CWSI.It is concluded that precipitation is the main factor affecting the decrease of CWSI in the Loess Plateau,and the significant increase of annual precipitation slows down the drought trend in the Loess Plateau.