Modelling the impact of increased street tree cover on mean radiant temperature across Vancouver’s local climate zones

《Modelling the impact of increased street tree cover on mean radiant temperature across Vancouver’s local climate zones》

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作者: Mehdi Aminipouri;Anders Jensen Knudby;E. Scott Krayenhoff;Kirsten Zickfeld;Ariane Middel

来源: URBAN FORESTRY & URBAN GREENING,Vol.39,Issue1,Pages 9-17

语言: 英文

关键字: Mean radiant temperature;Micrometeorological modelling;SOLWEIG;Urban greening

作者单位: Department of Geography, Simon Fraser University, Canada;Department of Geography, Environment and Geomatics, University of Ottawa, Canada;School of Environmental Sciences, University of Guelph, Canada;School of Arts, Media and Engineering, School of Computing, Informatics, and Decision Systems Engineering, Arizona State University, USA;Department of Geography, Simon Fraser University, Canada;Department of Geography, Environment and Geomatics, University of Ottawa, Canada;School of Environmental Sciences, University of Guelph, Canada;School of Arts, Media and Engineering, School of Computing, Informatics, and Decision Systems Engineering, Arizona State University, USA

摘要: Extensive impervious surface cover, anthropogenic heat emissions, and lack of vegetation contribute to the formation of distinct urban microclimates where higher air and surface temperature as well as lack of shade intensify outdoor heat exposure and thermal discomfort for humans. Modifications to the thermal environment via urban design can be used to mitigate this effect. In this study, the potential for increased street tree coverage to reduce mean radiant temperature (Tmrt)1 across six different local climate zones (LCZs)2 in Vancouver, Canada, was examined using the Solar and LongWave Environmental Irradiance Geometry (SOLWEIG)3 model. The radiant cooling effect of increased street tree coverage during the hottest day on record for Vancouver (July 29, 2009) was quantified by spatiotemporal changes to Tmrt. SOLWEIG was evaluated successfully prior to implementation of a street tree cover increase equivalent to 1% of plan area in each of six Vancouver LCZs investigated. Results indicate 3.2–6.3 °C reduction in spatially-averaged daytime (9:00 – 18:00) Tmrt and 3.3–7.1 °C reduction during the hottest period of day, 11:00-17:00. During the hottest period of day, the largest spatially-averaged Tmrt reduction (7.1 °C) was modelled in a low-rise residential area. Modelling suggested that a pedestrian standing directly under a tree canopy would experience Tmrt reductions of 15.5–17.3 °C in all LCZs. Also, under current conditions with no increase in tree cover, the compact high-rise and the large low-rise areas are shown to be the most and least comfortable environments regarding human thermal exposure with spatially-averaged Tmrt of 41.9 °C and 47.9 °C, respectively. We conclude that increases to Vancouver’s street tree cover by 1% of plan area can substantially reduce Tmrt during extreme hot weather. The results of this study show that the cooling potential of added street trees is greater in lower density residential neighborhoods with 1–2 storey buildings compared to higher density neighborhoods occupied by high-rise or mid-rise buildings.