中国遥感干旱指数时空特征及其对气候和地表覆盖变化的响应

干旱严重影响植被生长，威胁粮食安全，基于遥感计算的植被状态指数（Vegetation Condition Index，VCI）、温度状态指数（Temperature Condition Index，TCI）和植被健康指数（Vegetation Health Index，VHI）是常用的干旱指数，被广泛应用于干旱监测。为了探究近年来我国干旱特征及其对气候和地表覆盖变化的响应，分析了2003-2016年期间VCI、TCI和VHI的时空变化特征；采用最小二乘（OLS）和偏相关分析方法分析了这些指数对气候和地表覆盖变化的响应。基于上述干旱指数计算的干旱频率表明，中温带中部和南温带等地区干旱发生频率高，干旱指数变化趋势表明在2003-2016年期间中国大部分地区干旱缓解，但在中温带、南温带和高原气候区等局部地区干旱加剧；总体而言，干旱指数随着年平均温度的上升和年降水量的降低而减小，VHI与温度和降水量的相关性在不同气候区的一致性优于VCI和TCI；裸土的减少和植被的增加导致干旱指数增大，树木转变为低矮植被干旱指数降低。

Temporal and spatial patterns of remote sensing drought indices and their responses to climate and land use changes in China

Drought seriously affects vegetation growth and threatens food security. Vegetation condition index (VCI), temperature condition index (TCI) and vegetation health index (VHI) based on remote sensing have been widely used to monitor drought. In order to analyze spatial and temporal patterns of drought and their responses to climate and land use changes in China, this paper analyzed the temporal and spatial variations of VCI, TCI and VHI from 2003 to 2016; Least squares (OLS) and partial correlation analysis were used to analyze the responses of these indices to climate and land use changes. The drought frequency calculated using these drought indices indicated that drought occurred frequently in the central of middle temperate zone and southern temperate zone. The temporal trends of the drought indices indicated that drought was alleviated in most regions of China, but intensified in some areas such as the middle temperate zone, the southern temperate zone and the plateau climate zone during the study period. Overall, drought indices decreased with the increase of annual mean temperature and the decrease of annual precipitation. The correlations of VHI with temperature and precipitation were more consistent than VCI and TCI across different climate zones. The decrease of bare soil fraction and the increase of vegetation fraction led to the increase of drought indices. The conversion of trees to low vegetation induced the decreases of drought indices.