Strengthening of surface urban heat island effect driven primarily by urban size under rapid urbanization: national evidence from China

Abstract

ABSTRACT Surface urban heat islands (SUHIs) have received worldwide attention owing to their significant adverse impacts on socio-economic and environmental conditions. However, how the SUHIs vary across cities of different sizes and whether there is a threshold for city size that affect SUHIs were not explicit due to the limited selection of large cities in previous studies. Our study attempts to support comprehensive decision-making for national sustainable spatial management of SUHI in urbanized areas of different sizes. We used impervious surface area data to define the urbanized boundary for obtaining the SUHI in China. Then we analyzed the spatio-temporal patterns of SUHIs under China’s rapid urbanization. We furtherly constructed spatial autoregressive and structural equation models to verify the drivers’ direct and indirect contributions to SUHI. The SUHI effects existed extensively in most urbanized areas, not only in large or mega urbanized areas (average value: 2.08 ± 0.68°C) but also in petty urbanized areas (average value: 0.64 ± 0.19°C). We also found that the size of urbanized areas contributed the most to the increase in SUHI intensity (SUHII). Natural drivers are mediators indirectly contributing to variations in SUHII, influenced by anthropogenic drivers. In addition, we also found that the size of urbanized areas contributed the most to the increase in SUHI intensity (SUHII). The size of the urbanized areas had a positive non-linear relationship with SUHIIs. When the size was larger than 400 km2, the growth of SUHIIs maintained an equilibrium state. This study highlights the importance of impervious surface expansion for increasing SUHII. To confront SUHIs, it is necessary to perform proper urban planning.