Highlights
- An inverse thermal behaviour is observed for water and dense trees resulting in a relative nocturnal heating effect.
- The composition and abundance of surface covers are more influential in LSTs than spatial configuration.
- In urbanised areas, the cooling effects from trees are considerably undermined by heat transmitted by impervious materials.
- The influence of albedo from roof and pavements on the thermal profile of GITs should be further studied.
- Trees in rows or small clusters with well-irrigated grasses provided the best thermal cooling at day and night (up to 8 °C).
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.
