The cooling effects of hybrid landscapes at the district scale in mega-cities: A case study of Shanghai

Green spaces and water bodies can mitigate urban heat islands, and their cooling effects are influenced by certain characteristics and the surrounding environments. Under the influence of diverse built environments, what kinds of hybrid landscapes have a cooling effect, and which are ineffective? It is an essential issue to mitigate heat islands on the district scale, especially in mega-cities, and there remain fewer quantitative studies targeting it. This study developed a technical framework to analyze the cooling intensity and efficiency of hybrid landscapes in different built environments and took a typical mega-city, Shanghai, as an example. The samples were classified into five groups by characteristics of the built environment based on the proportions of buildings and their shadows. Furthermore, the efficient cooling intervals and the cooling intensities of hybrid landscape elements were identified based on their marginal effects. The findings showed that of all the elements, urban forests have a cooling capacity across various built environments, while water bodies and grasslands do not. In general, hybrid landscapes' cooling effects are weaker in districts with higher building density. This technical framework provides a way to mitigate heat islands in districts by planning hybrid landscapes, which can be generalized and be of practical value.