ABSTRACT

Vegetation has been considered as an effective strategy to combat the urban heat island effect. Most researches have focused on evaluating the cooling effect of trees in the urban thermal environment, while little attention has been paid to the cooling effect of the vegetation combinations. Moreover, most studies are focused on the horizontal cooling performance of plants, ignoring their vertical influence. Therefore, this study evaluates the 3D (horizontal and vertical) cooling performances of the three vegetation combination scenarios in the urban area using the ENVI-met model. The study indicates that the tree-grass (TG) combination has the best 3D cooling effect, followed by the tree-shrub-grass (TSG) combination, while the shrub-grass (SG) combination has the weakest 3D cooling effect. Besides, it is economical to plant TSG combinations because fewer trees are needed than planting TG combinations. Therefore, the study recommends the tree-shrub-grass combination rather than TG or SG combination in urban areas to effectively improve the thermal environment. The study also shows that the relationship between increasing tree coverage and the resulting cooling effect is not linear. The results of this study can effectively guide the design of greening strategies in urban areas to improve thermal comfort.

摘要

植被被认为是对抗城市热岛效应的有效策略。大多数研究都集中在评估城市热环境中树木的降温效果，而很少关注植被组合的降温效果。此外，大多数研究都集中在植物的水平冷却性能上，而忽略了它们的垂直影响。因此，本研究使用 ENVI-met 模型评估了市区三种植被组合情景的 3D（水平和垂直）降温性能。研究表明，树-草（TG）组合的3D降温效果最好，树-灌木-草（TSG）组合次之，灌木-草（SG）组合的3D降温效果最弱。除了，种植 TSG 组合是经济的，因为比种植 TG 组合需要更少的树木。因此，研究推荐城市地区采用树-灌-草组合而非TG或SG组合，以有效改善热环境。该研究还表明，增加树木覆盖率与由此产生的冷却效果之间的关系不是线性的。本研究结果可有效指导城市地区绿化策略的设计，以提高热舒适度。