Analysis of Urban Expansion and its Impacts on Land Surface Temperature and Vegetation Using RS and GIS, A Case Study in Xi'an City, China

The present study aims to explain the impacts of urban expansion on land surface temperature and vegetation of Xi'an City, China using integrated techniques of remote sensing (RS) and geographic information system (GIS). Urbanization is one of the potential driving factors for land use/land cover (LULC) change, vegetation decrease, and land surface temperature (LST) increase. To access information about the spatial and temporal land cover change, the use of two essential sources RS and GIS is indispensable. This study focuses on LULC changes in six districts of Xi'an City, China for the last three decades (1987-2018) using Landsat satellite images. The images from Thematic Mapper (TM), Enhanced Thematic Mapper (ETM+), and Operational Land Imager (OLI) of Landsat satellite are utilized. The results are as follows: (1) Xi'an experienced strong urbanization over the last 30 years with an increase of 69.6% in the urban area. The urban expansion pattern from 1987 to 2002 is alternate infilling and edge expansion in central districts, while from 2002 to 2018 is dominantly edge expansion toward outer districts. (2) Urbanization has negative effects on normalized difference vegetation index (NDVI); from 2002 to 2018 vegetation cover has decreased sharply in outer districts of Xi'an. (3) There is a synergetic relationship between urban expansion and LST. (4) The correlation between LST and NDVI is strongly negative, which indicates vegetation can relieve the effects of LST to some extent.