The time-evolving impact of tree size on nighttime street canyon microclimate: Wind tunnel modeling of aerodynamic effects and heat removal

Urban trees play a crucial role in urban climate many aspects. However, existing research has not adequately explored the impact from time-evolving perspective, that is, tree growth over time. To bridge this gap, study investigates wind tunnel effects of tree-to-canyon foliage cover and relative height (0.32–1.1 times canyon height), mimicking trees, on conditions street canyons during moderate extreme heat. The results reveal may affect canyon-wide ventilation heat removal two different scenarios. First, when are isothermal conditions, medium large fill half or reach slightly above canyon, decelerate shear layer weaken vortical flow, as result reducing ventilation. Second, trap at pedestrian level due to blockage air entrainment suppression upward buoyancy-driven flow ground surface. An temperature rise corresponds 1.5 °C full-scale setting is observed measurements. These observations suggest trees' must be managed for canyon's optimal nighttime.