CR 34:241-251 (2007)  -  DOI: https://doi.org/10.3354/cr00694

Urban heat islands in humid and arid climates: role of urban form and thermal properties in Colombo, Sri Lanka and Phoenix, USA

R. Emmanuel1,2,*, H. J. S. Fernando2

1Department of Architecture, University of Moratuwa, Moratuwa 10400, Sri Lanka
2Environmental Fluid Dynamics Program, Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, Arizona 85287-9809, USA

ABSTRACT: Using a micro-scale urban simulation program, we examined the sensitivity of air temperature and mean radiant temperature (MRT) of built-up urban cores to urban-area geometry (the density of buildings), thermal properties of human-made surfaces (albedo) and green cover (street trees), in 2 warm-climate cities: Pettah, Colombo (Sri Lanka) and downtown Phoenix, Arizona (USA). Air temperature and MRT are indicative of human thermal comfort, and their rural/urban gradients signify the urban heat island (UHI) effect. Although high albedo values lead to low daytime temperatures in both cities, the best thermal comfort, quantified by both the air temperature and MRT, was found in high-density development. Thus, density enhancement is a viable UHI mitigation option in built-up areas of warm climate cities. Manipulation of thermal properties is an alternative strategy, but the practical utility of high albedo surfaces is questionable. Additionally, some UHI mitigation options are more likely to bring improvements in MRT than in air temperature. Urban designers should use mitigation options that are based on human comfort, which is determined by both MRT and air temperature, rather than simply attempting to control air temperature alone.


KEY WORDS: Climate-sensitive urban design · Tropical climate · Desert climate · ENVI-met


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Cite this article as: Emmanuel R, Fernando HJS (2007) Urban heat islands in humid and arid climates: role of urban form and thermal properties in Colombo, Sri Lanka and Phoenix, USA. Clim Res 34:241-251. https://doi.org/10.3354/cr00694

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