Abstract: Exploring the spatial variability of urban thermal environment under the build-up area expansion is of great significance to better understanding of urban heat island (UHI) effect and improvement of urban ecological environment. Taking the built-up area of Xi’an as an example, the linear spectral mixing analysis method was used to extract the built-up area boundary using Landsat images of 2005, 2010 and 2016, and the space-time evolution of urban thermal environment was studied through the inversion of thermal infrared remote sensing image. In the meanwhile, based on the footprint of UHI effect and the information capacity technology derived from multidimensional histogram of image, the influence scope and spatial differentiation characteristics of UHI effect in urbanization were quantitatively investigated. Build-up area had a rapid expansion process, and impervious surface area increased significantly in Xi’an from 2005 to 2016. Urban construction enhanced the intensity and level of UHI effect in the study area along with the continuous expansion of build-up area, high-temperature areas increased and continuously overspread, gradually showing a flaky distribution characteristic. The spatial variability of the footprint of UHI effect in Xi’an was very prominent, and the influence range of UHI effect had progressively become small from 2005 to 2016. The information capacity could reflect the influence of urban expansion on the spatial heterogeneity of urban thermal environment, and the spatial heterogeneity of the urban heat island became more complicated with the increase of heat island intensity in Xi’an built-up area during the period of the study.

Key words: city, sustainable development, synergy, management optimization, energy-water-food-land-climate change nexus, conflict.