Green and Blue-space Significance to Urban Heat Island Mitigation

Kanchane Gunawardena, Tristan Kershaw

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It has long been recognised that cities exhibit their own microclimate and are typically warmer than the surrounding rural areas. This effect known as the urban heat island (UHI) results from the inadvertent modification of surface properties that lead to greater absorption of solar radiation, reduced cooling from slower wind speeds, and lower water evaporation rates. Cities contain fewer green and blue-spaces than rural areas, with the existing under constant threat from increasing population densities. The reduced water evaporation rates in cities as a result of the loss of such features is considered a major fac-tor in increasing the magnitude of the UHI. This paper seeks to identify the fun-damental principles of how green and blue-space affect canopy-layer and boundary-layer temperatures in the mitigation of urban heat risks. To address this, the paper presents a review of current understanding from city-planning, urban climatology, and heat island and climate change studies. The findings highlight recent research that suggests the cooling influence of both features are mainly relevant for canopy-layer conditions, with green-space offering greater heat stress relief when it is most needed. Any contribution to the cooling of the boundary-layer climate is attributed mainly to green-space increasing sur-face roughness that improves convection efficiency rather than evaporation, while little evidence exists for blue-space that support significant boundary-layer influence. This in turn has significant bearing on how these features should be used in future urban growth strategies that aim to deliver a reduced UHI and enhanced climate change resilience.
Original languageEnglish
Number of pages15
Publication statusPublished - Jun 2016
EventIntegrated Design at 50: Building our Future - University of Bath, Bath, UK United Kingdom
Duration: 30 Jun 20161 Jul 2016


ConferenceIntegrated Design at 50: Building our Future
Country/TerritoryUK United Kingdom


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