Contributions of natural and anthropogenic factors to summertime thermal environments across different urban scales: An investigation in Chengdu-Chongqing agglomeration, China

Understanding regional heat islands (RHIs) is important for initiating proper macro-interventions for mitigation and adaptation. However, limited studies have been conducted to reveal the underlying mechanisms and associated drivers. This study addresses this gap by analyzing RHI features and the contributions of anthropogenic and natural factors in the Chengdu-Chongqing area, China, at macro- (e.g., urban agglomeration, UA), meso- (e.g., metropolitan area, MA), and micro-scales (e.g., urban district, UR). This study verified the significant RHI growth in the Chengdu-Chongqing area, especially at the meso- and micro scales. For instance, the significantly increased areas at the macro scale accounted for 4 %, while those at the two meso-scale areas accounted for 7.0 % and 7.8 %, respectively. The proportions at the micro-scale were much higher. Anthropogenic factors contributed more than natural factors to RHI formation at the macro scale, while RHI growth at all scales was due to anthropogenic factors, and natural factors mainly contributed to RHI mitigation. Impervious surface density, population density, nighttime light intensity, precipitation, and the normalized difference vegetation index were the predominant contributors across all scales. Overall, this study explored the scale-dependent RHI and associated drivers from a multi-scale regional perspective and identified the critical areas for RHI mitigation.