Identifying the Effects of Vegetation on Urban Surface Temperatures Based on Urban–Rural Local Climate Zones in a Subtropical Metropolis

Abstract

Many studies have observed the crucial role of vegetated local climate zone (LCZ) types in mitigating the surface urban heat island (SUHI) effect. However, research analyzing the spatial variations in land surface temperature (LST) in a metropolis based on an urban–rural LCZ scheme and exploring the cooling effects of different vegetation types is still lacking. Here, our study focuses on the Guangzhou–Foshan metropolis and aims to elucidate the spatial variations in LST in subtropical cities and the regulating effect of vegetation on LST changes. We used a normalized difference vegetation index (NDVI) and LST data from space-borne MODIS products for the years 2000, 2009, and 2019, as well as LCZ maps, urban–rural gradient data, and land use and land cover (LULC) maps. Urban–rural, seasonal, daytime, nighttime, and diurnal comparative analyses were conducted using logarithmic regression, Pearson partial correlation, and comparison analysis. The results showed that LST values for built LCZ types were generally higher than those of land cover LCZ types, showing a positive correlation with building density and height. The LST decreased logarithmically across the urban–rural gradients, with a rapid decrease initially in the near-gradient urban area, followed by a flattening trend in farther-gradient suburban and rural areas. Regarding vegetated LCZ types, the NDVI metrics showed a significant negative correlation with the LST during the daytime but a positive correlation during the nighttime. The cooling effect of vegetated LCZ types was evident, with an average cooling amplitude of 1.92 °C over the three investigated years. In conclusion, urban LST changes are closely associated with LCZ types, urban–rural gradients, NDVI values, and vegetation types. The cooling ability of vegetation exhibited seasonal and diurnal variations, with a special emphasis on the cooling effect of dense evergreen broadleaf forests. Our findings offer valuable insights and can guide urban ecological construction and management by comprehensively assessing the impact of vegetation on urban surface temperatures.