基于TVDI的黄土高原干旱时空变化与其影响因素

Spatio-temporal Variation of Drought Characteristics and Its Influencing Factors in Loess Plateau Based on TVDI

为探讨黄土高原地区2001—2020年间干旱时空变化特征及其影响因素,利用MODIS增强植被指数(Enhanced vegetation index,EVI)以及地表温度(Land surface temperature,LST)数据,构建温度植被干旱指数(Temperature vegetation dryness index,TVDI)模型,探究黄土高原地区2001—2020年TVDI指数时空动态、变化趋势并利用地理探测器模型分析TVDI空间分异性的驱动因子。结果表明:2001—2020年间黄土高原TVDI空间分布具有较强的空间分异性,总体上呈现从西向东旱情逐渐增加的趋势,黄土高原多年平均TVDI为0.522,整体上处于轻旱状态。从TVDI多年变化趋势上分析,超过64%的区域有干旱加剧的趋势,且存在明显的地域分异规律,黄土高原西北部的内蒙古、宁夏北部以及山西部分地区旱情大多呈加剧趋势,而旱情缓解区域较为集中,多分布于陕西中部、宁夏南部和甘肃北部。各土地利用类型的TVDI年际变化均呈现不同程度上升的趋势且各土地利用类型年均TVDI差异明显,从大到小依次为:未利用地(0.571)、草地(0.554)、耕地(0.503)、林地(0.473)和建筑用地(0.462)。黄土高原地区TVDI的空间分异主要受高程、土壤类型、植被类型3个因子影响,三者q均超过0.3,是黄土高原干旱的主要驱动因素;在多因子交互作用下,高程与SIF组合对黄土高原干旱发生的影响力最强,q达到0.709。

To explore the spatio-temporal variation of drought characteristics in the Loess Plateau from 2001 to 2020 and its influencing factors,MODIS enhanced vegetation index(EVI)and land surface temperature(LST)data was used to establish the temperature vegetation dryness index(TVDI)model.The driving factors of TVDI in the Loess Plateau from 2001 to 2020 were analyzed by using Geodetector Model.The results showed that from 2001 to 2020,the spatial distribution of TVDI in the Loess Plateau had a strong spatial heterogeneity,and the drought increased gradually from west to east.The average TVDI of the Loess Plateau for the past 20 years was 0.522,indicating a light drought on the whole.According to the variation trend of TVDI,more than 64%of the regions showed a drying trend,and there was an obvious regional differentiation.The drought situation in Inner Mongolia,northern Ningxia and parts of Shanxi was mostly intensifying,while the areas of alleviating drought were concentrated,mainly distributed in central Shaanxi,southern Ningxia and northern Gansu.The annual change of TVDI of all land use types showed a rising trend in varying degrees,and the annual average TVDI of each land use type was significantly different,in order from large to small as follows:unused land(0.571),grassland(0.554),cultivated land(0.503),forest land(0.473)and construction land(0.462).The spatial differentiation of TVDI in the Loess Plateau was mainly affected by three factors:elevation,soil type and vegetation type,whose q values were all exceeding 0.3,which were the main driving factors of drought in the Loess Plateau.Under the interaction of multiple factors,the combination of elevation and SIF had the strongest influence on the occurrence of drought in the Loess Plateau,with q value reaching 0.709.