A hierarchical analysis of the relationship between urban impervious surfaces and land surface temperatures: spatial scale dependence, temporal variations, and bioclimatic modulation

Context Understanding how urban impervious surfaces (UIS) affect land surface temperatures (LST) on different scales in space and time is important for urban ecology and sustainability. Objectives We examined how spatial scales, seasonal and diurnal variations, and bioclimatic settings affected the UIS-LST relationship in mainland China. Methods We took a hierarchical approach explicitly considering three scales: the ecoregion, urban cluster, and urban core. The UIS-LST relationship was quantified with Pearson correlation using multiple remote sensing datasets. Results In general, UIS and LST were positively correlated in summer daytime/nighttime and winter nighttime, but negatively in winter daytime. The strength of correlation increased from broad to fine scales. The mean R-2 of winter nights at the urban core scale (0.262) was 4.03 times as high as that at the ecoregion scale (0.065). The relationship showed large seasonal and diurnal variations: generally stronger in summer than in winter and stronger in nighttime than in daytime. At the urban core scale, the mean R-2 of summer daytime (0.208) was 3.25 times as high as that of winter daytime (0.064), and the mean R-2 of winter nighttime (0.262) was 4.10 times as high as that of winter daytime (0.064). Vegetation and climate substantially modified the relationship during summer daytime on the ecoregion scale. Conclusions Our study provides new evidence that the UIS-LST relationship varies with spatial scales, diurnal/seasonal cycles, and bioclimatic context, with new insight into the cross-scale properties of the relationship. These findings have implications for mitigating urban heat island effects across scales in China and beyond.