中文摘要：

季节性干旱是影响关中平原农业生产最主要的灾害，研究气候变化背景下的关中平原旱情空间分布特征和变化规律具有重要的科学意义与应用价值。基于关中平原2003--2014年每年3月上旬-5月下旬的旬时间尺度条件植被温度指数（VTCI）的干旱监测结果，采用结构相似度（SSIM）研究关中平原VTCI的空间变化特征及其影响因子。结果表明：关中平原VTCI的空间变化特征具有明显的区域差异性和空间异质性，结构性因素是VTCI空间变化的主要影响因子，总体上受水热、地形分布格局等因素的结构性影响，但微地貌、下垫面覆盖的不同及变化和人为因素导致其主体产生变化。当微地貌、下垫面覆盖类型和人为因素成为主导因子时，结构相似度与其高度相关，对其变化的响应非常敏感。与利用某些指数直接作为干旱的指示因子或构建统计模型分析干旱特征相比，引入研究图像的结构信息的参量SSIM实现了定量、准确、形象地描述干旱的空间分布特征和变化规律。

英文摘要：

Seasonal drought is a main disaster for agricultural production in Guanzhong Plain, and research on spatial distribution characteristics and variation patterns of droughts under the global climate change is of great theoretic significance and applied value. Based on time series of drought monitoring results of vegetation temperature condition index （VTCI） from early March to late May during 2003 to 2014, the structural similarity （SSIM） was applied to analyze spatial characteristics of the time series of VTCI in the plain, and impact factors which affecting the spatial characteristics were analyzed as well. The results showed that the spatial characteristics of VTCI in Guanzhong Plain had distinctive regional variations and spatial heterogeneity, and the structural factor was the main factor affecting the variations. In general, the spatial variations of VTCI were influenced by the distribution pattern of water and heat conditions and terrain, as well as the microtopography, the underlying surface and the human factor. The variations were highly correlated and very sensitive to the changes in the microtopography, the underlying surface or the human factor when they became the dominant factors. Compared with other analytical methods that used some indexes as the indicators of droughts or made statistical models, the SSIM which has the structure information of images was a better approach for indicating the spatial characteristics of the droughts and their variations quantitatively, accurately and conveniently.