Abstract
The Urban Heat Island (UHI) effect can result in higher urban densities being significantly hotter (frequently more than 4 °C, even up to 10 °C) compared to their peri-urban surroundings. Such artificial heat stress increases the health risk of spending time outdoors and boosts the need for energy consumption, particularly for cooling during summer. Urban structure, land cover and metabolism are underlined as key contributors in city scale. Under question is which urban configurations can make urban precincts and their microclimates more resilient to the surface layer Urban Heat Island (sUHI) effect? The City of Sydney is increasingly experiencing the UHI effect due to its numerous urban development projects and changes in climate. In the Sydney context, this ongoing research aims to explore the most heat resilient urban features at precinct scale. It covers five high density precincts in central Sydney and is based on a nocturnal remote-sensing thermal image of central Sydney taken on 6 February 2009. Comparing the surface temperature of streetscapes and buildings’ rooftops (dominant urban horizontal surfaces), indicates that open public spaces and particularly streetscapes are the most sensitive urban elements to the sUHI effect. The correlations between street network intensity, open public space plot ratio, urban greenery plot ratio and sUHI effect is being analysed in Sydney’s high density precincts. Results indicate that higher open space plot ratio and street network intensity correlate significantly to higher sUHI effect at precinct scale. However, higher urban greenery plot ratio can effectively mitigate the sUHI effect in high density precincts.
Highlights
Cities are anticipated to accommodate up to 70% of the global population by 2050 (DESA, 2012)
Facing the Urban Heat Island (UHI) effect, the City of Sydney has facilitated a number of UHI investigations based on remote sensing thermal imagery over the past decade, concluding with a Building Thermal Performance Index (BTPI) to evaluate buildings’ envelope thermal behavior (Samuels, Randolph, Graham, McCormick, & Pollard, 2010)
Utilizing the literature on the UHI effect, thermal imagery, GIS information and image processing, this study aims to investigate the correlations between the urban greenery ratio, open space ratio and the surface temperature in five precincts in central Sydney
Summary
Cities are anticipated to accommodate up to 70% of the global population by 2050 (DESA, 2012). Compared to the current urbanization rate of 50%, almost all the expected global population growth will be accommodated in cities Such rapid urbanization means higher densities in existing cities and many more new urban areas to accommodate up to 2 billion new urban dwellers. Climate change projections indicate a likely increase of 2 to 5 °C in Australian surface temperature by 2050 (CSIRO, 2007; OECD, 2010). SUHI research indicates that high density building blocks can magnify the sUHI effect in cities by increasing the opportunity for surface materials to absorb direct and reflected sunlight radiation (Erell, Pearlmutter, & Williamson, 2011; Giridharan, Lau, Ganesan, & Givoni, 2007; Priyadarsini, 2009). According to Campoli and MacLean’s (2007) classification of building density, over 100 units per acre can be considered as very high building density
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