Strengthening of Surface Urban Heat Island Effect Driven Primarily by Urban Size Under Rapid Urbanization: Empirical Evidence From China

Context Surface urban heat islands (SUHIs) have received worldwide attention owing to their significant adverse impacts on socio-economic and environmental conditions. Although SUHI patterns have been studied previously, how the SUHIs change across cities with different sizes and whether there is a threshold of city size for affecting SUHIs remains poorly understood. Objectives The primary objective is to facilitate more appropriate and effective planning of SUHI mitigation in urbanized areas of different sizes. Methods The SUHI effects were deployed to surface urban heat island intensity (SUHII). we systematically analyzed the spatio-temporal patterns of SUHIs at the national scale under the conditions of China’s rapid urbanization, and explored the impact of natural and anthropogenic factors on SUHI by spatial error model. Results Intense urbanization occurred in China between 2000 and 2015, primarily dominated by the expansion of petty and mega urbanized areas. The SUHII gradually increased at the national scale from 2000–2015, and SUHIs also appeared in petty urbanized areas. We also found that the size of urbanized areas contributed the most to the increase in SUHII. In addition, the size of the urbanized areas had a positive non-linear relationship with SUHIIs, and when the size was larger than 400 km2, the growth of SUHIIs maintained an equilibrium state. Conclusions Urban expansion is occurring rapidly. This study highlights the importance of impervious surface expansion for increasing heat island intensity. To confront SUHI effects, it is necessary to reduce the fragmented distribution of small towns and increasing green infrastructures.