斑块面积对城市绿地降温效应的影响研究进展

Abstract

在气候变化和快速城市化的双重影响下，全球城市面临日益加剧的热岛效应。绿地能够有效改善城市热环境。城市土地资源紧缺，优化绿地布局，使有限面积的绿地发挥更大的降温效果具有重要的理论意义和实践价值。其中，如何设置绿地斑块大小则是优化绿地布局的首要考虑因素之一。从斑块和景观的尺度总结了现有绿地斑块大小对其降温效应影响的研究进展，结果表明：1）在斑块尺度，随着绿地斑块面积增加，绿地的降温效应相应增加，但增加的趋势为非线性变化，表现为温度随绿地斑块面积的增加先下降，后趋于平稳，表明可能存在降温效率（单位面积绿地降温能力）最强的斑块大小；2）在景观尺度，绿地斑块大小在空间上的配置对热环境的影响研究结果存在差异，尚无一致性定论。基于已有研究，本文指出了现有绿地斑块大小对其降温效应影响研究中的问题与不足：1）主要关注绿地斑块大小与温度的统计关系，缺乏对其具体影响过程和内在机制的深入探讨；2）更多关注地表温度，而对与人体舒适度和健康直接相关的其他热环境指标的研究较少；3）研究中缺少对城市中数量巨大，分布最广的小型绿地斑块的考量。未来的研究应加强从遮阴和蒸腾等降温过程深入解析绿地斑块大小对热环境影响的内在机理机制，从降温效率的角度，探讨是否存在最优的斑块大小，并进一步探讨绿地周围建筑环境对绿地斑块大小与其降温效应关系的影响，为优化城市绿地分布，改善城市热环境提供科学依据。;In the context of global climate change and rapid urbanization, the urban heat island effect has been aggravated in many cities around the world. Green space can effectively improve the urban thermal environment. As land resources in the city are scarce, optimizing the layout of green space and making the limited green space offer a greater cooling effect has the important theoretic significance and practical worth. How to set the green patch size is one of the first considerations for optimizing the green space pattern. In this paper, we summarized exiting research about influences of green patch area on its cooling effect from the patch and landscape scale, respectively. At the patch scale, the cooling effect of green space nonlinearly enhanced with increasing patch area. Specifically, as the green patch size increased, the temperature decreased firstly and then leveled off. The optimal patch size, which had the strongest cooling effect per unit area green space, may exist. At the landscape scale, effects of the spatial layout of the size of green patch on the urban thermal environment varied considerably across studies. In addition, this paper pointed out some problems and shortcomings of existing relevant studies:1) Most of the studies focused on the statistical relationships between green patch area and temperature, while studies about the specific influence processes and mechanisms under those relationships were scare; 2) Most of the studies focused on the land surface temperature, but other thermal environmental indicators that directly related to human thermal comfort and health risk were ignored; 3) Small green patches, the main component of urban green space, were not included in most current studies. We further highlighted a few research directions or questions that should be paid attention in the future:1) Analyzing the internal mechanism of effects of green patch area on urban thermal environment from the perspective of cooling processes (shade and transpiration); 2) Exploring how the cooling efficiency (cooling effect per unit area green space) change with the patch area, and detecting the optimal patch size; 3) Investigating influences of urban structure (building) around the green space on the relationship between green patch size and its cooling effect. To explore and/or answer these research questions can effectively further reveal specific effects of green patch size on the urban thermal environment, and thus provide important scientific bases for planning the spatial layout of urban green space, enhancing the cooling efficiency of green patches, and improving the thermal comfort of cities.