Alliance for Community Trees News

Effect Of Shade Trees On Cooling The Built Environment

By Conni Kunzler | August 14, 2017

Source: RubyUpreti, Zhi-HuaWang and JiachuanYang, “Radiative shading effect of urban trees on cooling the regional built environment,” Urban Forestry & Urban Greening

Tempe, AZ (May 31, 2017) – Land use and land cover changes from urbanization have led to significant modifications in the built environment — and the need for urban trees to help mitigate heat. New research shows that the cooling effect of urban shade trees is most prominent during the night time.

Land use and land cover changes due to urbanization have led to significant modifications in the built environment at both local and regional scales, making adaptation/mitigation strategies imperative for the sustainable development of cities.

While urban trees offer great potential for heat mitigation and enhanced environmental quality, most of the existing urban land surface models do not contain adequate representations of trees, particularly the radiative heat exchange in the canyons.

In this study, researchers incorporated the radiative shading effect of urban trees into the state-of-the-art version of the coupled Weather Research and Forecasting-Urban Canopy Model modeling system. This modeling framework, albeit at its infancy, is applied to the Phoenix Metropolitan area to study the regional cooling effect of trees in an arid environment.

Simulation results demonstrated the capacity of urban trees in reducing urban surface and air temperature by about 2 ∼ 9 °C and 1 ∼ 5 °C respectively and increasing relative humidity by 10 ∼ 20% during a mean diurnal cycle; the effect is more prominent during nighttime.

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