Spatial heterogeneity of the thermal environment based on the urban expansion of natural cities using open data in Guangzhou, China

The change in the urban thermal environment resulting from urban expansion is attracting increasing attention from researchers. In this research, the influence of the urban expansion process on the spatial heterogeneity of the thermal environment was analyzed, including quantitative research on urban expansion based on the natural city (NC) concept using open data and the footprint of the thermal environment (TE FP) model to reveal the influences in different time periods between 2014 and 2018 in Guangzhou, China. And the TE FP is an indication used to evaluate whether certain area is affected by the thermal environment of the NC. The results demonstrated the following. (1) The high-temperature area in Guangzhou was 2293.55 km(2) in 2014, 2330.24 km(2) in 2016, and 2609.81 km(2) in 2018 and expanded by 1.60% (2014-2016), 12.00% (2016-2018) and 13.79% (2014-2018), respectively. (2) The urban area increased from 182.10 km(2) in 2014 to 266.90 km(2) in 2018, which represented an increase by almost half, with an average annual expansion rate of 10.03%. (3) In 2014, 2016 and 2018, the area representing the TE FP consisted of the areas of five buffer zones, six buffer zones and eight buffer zones, respectively. This study provides a new approach to the study of urban expansion and a new perspective for exploring the influence of the urban expansion process on the spatial heterogeneity of the thermal environment.