Effects of urban geometry on thermal environment in 2D street canyons: A scaled experimental study

Abstract

Changes in urban geometry significantly alters the urban microclimate. Suitable urban geometrical layouts can effectively improve the urban thermal environment to achieve a more sustainable and healthier city. A quantitative assessment of the relationship between the urban geometry and thermal environment is essential to provide scientific guidance for better urban and building design. Hence, we performed a scaled outdoor measurement to investigate the diurnal variations in air, and west and east wall temperatures within two-dimensional (2D) street canyons. We adopted the daily average temperature T‾, daily temperature range DTR, and hottest time tmax to describe the diurnal temperature characteristics. The influence of aspect ratios was considered (building height/street width, H/W = 0.5, H = 0.5 m, and H/W = 1, 2, 3, 6, H = 1.2 m). Canyon air experienced a smaller T‾ and DTR compared with the east and west walls. With an increase in the aspect ratio, no significant difference was observed in the T‾ of canyon air. The east and west walls of H/W = 2, 3, and 6 experienced lower T‾ (26.1–26.9 °C) and smaller DTR (11.7–18.4 °C) than those of H/W = 0.5, 1 (T‾=26.7–28.7 °C and DTR = 16.0–26.1 °C). A higher phase lag of tmax occurred between H/W = 0.5, and H/W = 6. As the aspect ratio increased, the differences in T‾, DTR, and tmax between the east and west walls decreased. This study improves our understanding of how urban morphology influences urban thermal environment and provides meaningful references for urban planning. Such high-quality experimental data can be used to validate and further improve numerical simulations and theoretical models.