Spatial distribution and influencing factors on urban land surface temperature of twelve megacities in China from 2000 to 2017

Abstract

China witnessed a rapid urbanization progress in the past 20 years. Urbanization can greatly influence urban environment, especially thermal environment. Causes for urban heat island (UHI) formation vary in different climatic regions. Understanding characteristics of spatial distribution of urban land surface temperature (ULST) and influencing factors of UHI formation is important for sustainable urban development. In this study, twelve megalopolises in China, each with a population over 5 million, were selected as research sites. Built-up areas and ULST of these megalopolises were extracted from remote sensing data of earth observation satellites of Landsat program for the three periods of 2000–2017. Spatial variation characteristics of ULST were analyzed. Influences of soil moisture, surface water availability, surface albedo, vegetation, energy consumption, gross domestic product, latitudes, precipitation, topography, and distance to the downtown on ULST were investigated through multivariate regression analysis. Results show that: all the cities expanded continuously from 2000 to 2017, but expansion rates varied significantly among the megalopolises. Urban expansion has significant effects on the spatial distribution of ULST. ULST changes more quickly when the expanded area and expansion rate are higher. Simultaneously, spatial distribution of ULST was found to relate to the shape of an urban boundary. Circularly expanding cities showed the most concentrated distribution of high-temperature regions. Correlation analysis revealed that surface water use, evapotranspiration, electric energy consumption, surface albedo, and vegetation activity were the primary influencing factors on ULST, while GDP, latitude, distance, and precipitation had no significant effects on ULST. Among the primary influencing factors, surface water was the main controlling factor on ULST in cities with more surface water distribution. Building area played a more important role in ULST in cities with less surface water distribution. In addition, vegetation area played a relatively more important role in ULST in semi-humid cities than humid cities.