Abstract
Urban areas are characterized by a large proportion of artificial surfaces, such as concrete and asphalt, which absorb and store more heat than natural vegetation, leading to the Urban Heat Island (UHI) effect. Cool pavements, walls, and roofs have been suggested as a solution to mitigate UHI, but their effectiveness depends on local land-use patterns and surrounding urban forms. Meteorological data was collected using a mobile platform in the Power Ranch community of Gilbert, Arizona in the Phoenix Metropolitan Area, a region that experiences harsh summer temperatures. The warmest hour recorded during data collection was 13 August 2015 at 5:00 p.m., with a far-field air temperature of about 42 ∘ C and a low wind speed of 0.45 m/s from East-Southeast (ESE). An uncoupled pavement-urban canyon Computational Fluid Dynamics (CFD) model was developed and validated to study the microclimate of the area. Five scenarios were studied to investigate the effects of different pavements on UHI, replacing all pavements with surfaces of progressively higher albedo: New asphalt concrete, typical concrete, reflective concrete, making only roofs and walls reflective, and finally replacing all artificial surfaces with a reflective coating. While new asphalt surfaces increased the surrounding 2 m air temperatures by up to 0.5 ∘ C, replacing aged asphalt with typical concrete with higher albedo did not significantly decrease it. Reflective concrete pavements decreased air temperature by 0.2–0.4 ∘ C and reflective roofs and walls by 0.4–0.7 ∘ C, while replacing all roofs, walls, and pavements with a reflective coating led to a more significant decrease, of up to 0.8–1.0 ∘ C. Residences downstream of major collector roads experienced a decreased air temperature at the higher end of these ranges. However, large areas of natural surfaces for this community had a significant effect on downstream air temperatures, which limits the UHI mitigation potential of these strategies.
Highlights
Across the world, urbanization is characterized by the replacement of natural land cover with artificial materials, such as asphalt and concrete, in the form of walls, roofs, and pavements
CLUHI, which refers to the air temperature difference 2 m above the ground, is significant because it is the height at which most outdoor activities takes place
The present study investigates the potential benefits of using cool surfaces to mitigate Urban Heat Island (UHI) in the Power Ranch community in the Phoenix Metropolitan Area in Arizona, USA
Summary
Urbanization is characterized by the replacement of natural land cover with artificial materials, such as asphalt and concrete, in the form of walls, roofs, and pavements. This leads to the spatial growth of cities and an increase in impervious surfaces, a phenomenon called urban sprawl [1,2]. Previous studies have demonstrated the effect of urban sprawl on public health [6,7], flora and fauna [8,9], air quality [10], and urban water use [11,12,13]. Unless otherwise stated, UHI refers to CLUHI
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