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<p>Urban anthropogenic heat has a direct impact on urban climate. However, due to a warm feedback loop, the attributions of urban anthropogenic heat in urban area are unclear. This research carried out an attribution analysis of anthropogenic heat index (AHI) derived from remote sensing over global 1386 cities to investigate the contribution of 13 environmental variables to global urban anthropogenic heat based on GEE environment. 13 independent variables are categorized the groups of human activities, land morphology, vegetation, climate and atmospheric environment on anthropogenic heat. The results show that although human activities are considered as the main source of the anthropogenic heat, other factors have more impacts on the anthropogenic heat pattern in the urban area due to the feedback loop of urban thermal environment. Climate played a leading role in the impacts on anthropogenic heat with a contribution rate of 30-50% in most background contexts. The impact rate of human activities and landforms on anthropogenic heat accounts for 20% in most background scenarios. The findings of this research can contribute to the solution of mitigating urban anthropogenic heat and expanded the research scope of urban anthropogenic heat in the urban area.</p>

Albedo is one of the key parameters in the surface energy balance and it has been altered due to urban expansion, which has significant impacts on local and regional climate. Many previous studies have demonstrated that changes in the urban surface albedo are strongly related to the city’s heterogeneity and have significant spatial-temporal characteristics but fail to address the albedo of the urban surface as a unique variable in urban thermal environment research. This study selects Beijing as the experimental area for exploring the spatial-temporal characteristics of the urban surface albedo and the albedo’s uniqueness in environmental research on urban spaces. Our results show that the urban surface albedo at high spatial resolution can better represent the urban spatial heterogeneity, seasonal variation, building canyon, and pixel adjacency effects. Urban surface albedo is associated with building density and height, land surface temperature (LST), and fractional vegetation cover (FVC). Furthermore, albedo can reflect livability and environmental rating due to the variances of building materials and architectural formats in the urban development. Hence, we argue that the albedo of the urban surface can be considered as a unique variable for improving the acknowledgment of the urban environment and human livability with wider application in urban environmental research.

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