Analyzing spatio-temporal characteristics of urban LULC and LST over Shanghai during 2009-2019

Abstract

The expansion of urban areas is always accompanied by land use/land cover (LULC) changes and associated with the distribution of urban heat islands (UHI) simultaneously. In particular, in the metropolis such as Shanghai, the land cover transitions between the impervious surface (IS) and vegetation areas highly influence the ecological quality. This study focused on the monitoring and analysis on the LULC and land surface temperature (LST) spatio-temporal changes in Shanghai during the period between 2009 and 2019. We evaluated LULC and LST changes based on the multitemporal Landsat images acquired over five individual years (i.e., 2009, 2012, 2015, 2017 and 2019). In particular, the Fully Constrained Least Squares (FCLS) spectral unmixing and several derived spectral indices are used for generating the LULC maps, and Radiative Transfer Equation (RTE) temperature inversion method is utilized for estimating the LST. In order to compare the dominance of different land classes, then we analyzed the classification maps from different landscape levels. Experimental results demonstrate that during the past ten years the IS of Shanghai continually expanded from the city center mainly towards the Pudong, Songjiang and Jiading three districts directions. Vegetation especially the cropland in the urban fringe areas were replaced by the newly appeared IS, which lead to the rising temperature in the corresponding areas. This may further accelerate the urban heat island phenomenon.