Assessing the impact of fractional vegetation cover on urban thermal environment: A case study of Hangzhou, China

The large-scale urbanization has changed the surface characteristics of cities, seriously affected the urban heat balance, and worsened the urban thermal environment. The regulation of vegetation coverage on urban climate has received extensive attention. This study aims to assess and predict changes in the urban thermal environment of Hangzhou by monitoring the variation of the urban thermal field variance index (UTFVI) affected by fractional vegetation cover (FVC) changes. The results indicate that the area of high level FVC will likely decrease by 52.91%, while the area of lower level FVC will likely increase by 33.83% from 1990 to 2030. Furthermore, the area of the strongest level UTFVI shows a significant trend of expansion, increasing by 467.299 km2 from 1990 to 2030, while the area of other levels UTFVI shows different degrees of decrease. Specifically, the area of strong and stronger levels UTFVI decreased by 149.641 km2 and 271.464 km2, respectively. The spatial correlation between the FVC and UTFVI changes is significant and negative, with p-values less than 0.01 and negative coefficients. The absolute value of the coefficient will decrease from 0.416 to 0.246 from 1990 to 2030, and the correlation between FVC and UTFVI changes shows a decreasing trend. The linear regression analysis demonstrates a significant negative correlation between the FVC and UTFVI, with coefficients ranging from −0.470 to −0.280 and p-values less than 0.001, further indicating that the FVC has a mitigating effect on the urban thermal environment. This study provides new insights into thermal environment governance and urban sustainable development.