Understanding the coupling effect of urban structure, vegetation and landscape on Surface Urban Heat Island (SUHI) in Europe

The past century has seen dramatic increases in global temperatures and mounting urbanization. As a result of these events, the surface urban heat island (SUHI) effect has received growing attention in scientific research worldwide. However, its global expansion trend and impact mechanisms have not yet been sufficiently explored. A global search was initially conducted to collect all available relevant publications, and semantic analysis was performed to extract all cities affected by the SUHI to understand how the phenomenon is expanding globally and impacting more cities in different geographic areas. The Shannon evenness index was employed to identify the spatial locations (hotspots) across the globe where UHI-related research has been concentrated in multiple cities over the last 120 years. Finally, Europe was selected as a testbed as it contains the most hotspots for conducting an analysis to understand the coupling effect of vegetation structure, urban structure and landscape on land surface temperature (LST). Multiple data sources were investigated, including the vegetation structure-related NDVI, biomass, tree height and tree cover density; urban structure-related building height, imperviousness density, building compactness and road density; and urban landscape-related latitude, longitude, heterogeneity, and population density. We obtained 788 European functional urban areas and their respective urban cores, and then extracted mean values of impact features. Feature importance analysis, using SHAP, allowed us to assess the primary drivers of SUHI across Europe. The coupling relationship between LST and impact features highlights the need for systematic planning of urban landscapes. This study will undoubtedly be of interest to scientists investigating the SUHI effect and its trends. Stakeholders will acquire a broader perspective and deeper understanding of SUHI in order to engage in more effective urban planning to offset and mitigate the phenomenon's adverse effects in the context of increasing climate change and urbanization.