Assessing Long-Term Thermal Environment Change with Landsat Time-Series Data in a Rapidly Urbanizing City in China

The studies of urban heat islands or urban thermal environments have attracted extensive attention, although there is still a lack of research focused on the analysis of long-term urban thermal environment change with fine spatial resolution and actual exposure of urban residents. Taking the rapidly urbanizing city of Nanjing, China as an example, this study utilizes the Landsat-derived daytime time-series land surface temperature data to comprehensively assess the city's long-term (30-year) urban thermal environment change. The results showed that: (1) The overall surface urban heat island intensity showed a noticeable trend of first increasing and then decreasing from 1990 to 2020. (2) It exhibited the detailed spatial distribution of urban heat/cold islands within the urban center boundary. The percentage of surface urban heat islands was 77.01% in 1990, and it increased to 85.79% in 2010 and then decreased to 80.53% in 2020. (3) More than 65% of the urban residents have lived in areas with a surface urban heat island intensity greater than 3.0 degrees C, which also showed a trend of first increasing and then decreasing from 1990 to 2020. The methods and findings of this study can provide a reference for other studies on urban thermal environment changes and urban sustainable development.