Comparative and combinative cooling effects of different spatial arrangements of buildings and trees on microclimate

The amounts and arrangements of buildings and trees are primarily responsible for controlling small-scale thermal environments. However, uncertainties exist about how such structures regulate microclimates in cities. We investigated the effects of three contributory factors on microclimates: building arrangement, amount of land covered by tree canopies, and the intensity of solar irradiation relative to latitude. We modeled microclimate with the high spatial and temporal resolution ENVI-met model and validated it with in situ measurements. We designed and modeled seventy-two idealized model scenarios to compare cooling effects of various combinations of the contributory factors to microclimate. We found that (1) both building and tree arrangements influence thermal microclimates (i.e., high-rise developments provide more land for greenspace and lead to lower near-surface temperatures than low-rise developments), (2) more area of forested greenspace leads to a more significant cooling effects (but the cooling effect of forested greenspace is non-linear relative to area), and (3) intense solar irradiation suppresses the cooling effects of greenspaces. Our results underscore the practical implications of shading arrangements on the evolution of thermal environments in high-density cities, which is useful for planning and designing mitigation strategies in urban areas and developing action plans at the neighborhood scale.