基于绿化指标的城市绿地降温效应研究进展

城市化使城市下垫面属性改变，人工表面取代自然地表，导致室外热环境恶化，其形成的城市热岛效应引发的异常气候问题严重危害人类的生命健康。研究已证实植被可以通过遮荫和蒸腾等作用产生降温的生态效益，但其产生的生态效益与植被的规模或种类或分布方式等之间的联系仍没有明确量化掌握。目前，通过不同指标对绿地特征进行概括，从而精准量化绿地对室外热环境的调节作用已成为研究重点。对绿地面积、绿化覆盖率、绿地率、乔木覆盖率、三维绿量以及天空可视度六种指标调控室外热环境的研究进行综述：首先分析各绿化指标之间的区别，并分别论述各绿化指标与热环境相关研究，总结各指标在量化降温效应的特点及局限性。之后提出绿化指标互补量化研究方法，从三维空间视角为完善绿量指标研究提出三维绿量体以及三维绿量体与热环境关系研究的相关方式，从而精确地对三维绿量在空间中地具体分布进行表达，更加真实地反映绿地的植被特征。根据以往针对三维绿量的研究提出三维绿量阈值，结合三维绿量的空间分布及树种差异性，挖掘影响绿地降温效应的潜在影响因素，以便更好地量化绿地降温效果，充分发挥城市绿地的生态效益。最后论述绿视率这一新的量化指标在量化绿地降温效应的潜力，以期推动绿视率与热环境相关研究。

Research progress on cooling effect of urban green space based on greening index

Urbanization changes attributes of urban underlying surface; artificial surface replaces natural surface, resulting in deteriorations of outdoor thermal environment. Abnormal climate issues caused by urban heat island effect seriously threaten human life and health. It is confirmed that vegetation generates cooling effects via shading and transpiration. However, quantitative relationships between this kind of ecological benefit and scales, species or distributions of vegetation are not clear yet. At present, studies focus on accurate regulation of green spaces on outdoor thermal environments. In this study, six greening indicators, including green area, green coverage rate, green coverage rate, tree coverage rate, three-dimensional green quantity and sky view factor, were reviewed on regulating outdoor thermal environment. Firstly, it was focused on various greening indicators, including their differences, correlation between them and outdoor thermal environments, and quantified cooling effect and limitation. Secondly, it was proposed complementary-quantitative method of greening indicator in which green volume and research paradigm on itself and outdoor thermal environments were included in order to precisely express spatial information of green volume and features of vegetation in green space. It was also proposed threshold of green volume; influencing factors on cooling effects were studied deeply based on distributions of green volume and difference between species, in order to quantify the cooling effect of green space more accurately and benefit its ecosystem services. At last, capacity of green view index on cooling effects of green space was addressed to promote studies on relevance between this new indicator and outdoor thermal environment.