Quantifying the seasonal cooling capacity of ‘green infrastructure types’ (GITs): An approach to assess and mitigate surface urban heat island in Sydney, Australia

Abstract

Green infrastructure (GI) can help moderate urban overheating and mitigate surface urban heat islands (SUHIs) by providing protection from solar radiation, cooling surfaces through evapotranspiration, and modifying heat exchanges through advection. However, more research is needed to determine the optimum amounts, compositions and configurations of GI necessary to provide maximum thermal cooling and mitigate urban warming more effectively. In this study, a recently developed ‘green infrastructure typology’ (GIT) scheme is applied in Sydney, Australia to analyse the interplay and cumulative cooling effects of natural and artificial elements in summer and winter by considering their morphological and spatial characteristics. Thermal-vegetation index (TVX), simple linear regression and correlation analyses were performed to identify factors that are more influential on the cooling effects of GI. After, a hierarchical cluster analysis was performed to group types with similar cooling capacity, representing potential mitigation strategies that could be implemented at local scale. Results presented here demonstrate that the cooling effect of different types of GI on surface temperatures mostly depend on the abundance and composition of natural and man-made features. As thermal performance of GI depends on the interplay between both, this study offers a more holistic and integrated approach to assess and counter urban overheating. Key insights derived from the analysis are presented to provide a better understanding on which aspects of GI and urban form should be considered to mitigate SUHIs more effectively in neighbourhoods urban precincts and streets.