基于形态学空间格局分析的城市绿地对热环境的影响研究

城市绿地是改善热环境的重要方式之一,当前研究主要集中于以景观指数衡量的绿地空间形态与热环境之间的关系,较少关注以城市公园为主的绿地内部空间结构对热环境的影响及其规划设计实施的可操作性。基于另一种视角——形态学空间格局分析的7个指标量化绿地空间格局,以武汉主城区的其中25个绿地为研究对象,通过2018年9月15日Landsat 8遥感数据反演地表温度,从绿地的点面、边界、廊道三方面分析绿地空间格局对绿地内部平均温度(T)、降温幅度(ΔT)的影响。结果表明:25个绿地可分为内外降温显著型、内部降温显著型、降温效果一般型、降温能力较弱型4类绿地,它们具有显著差异的空间格局主要集中在核心、孤岛与分支。绿地空间格局对自身温度的影响上,T与核心、孔隙指标显著负相关,与孤岛、分支指标显著正相关,可通过提高绿地核心斑块的集中性、核心斑块内部边界营造、减少破碎化小斑块数量、避免仅一端连接核心斑块的廊道等措施,提高绿地自身的降温效果。环线、桥接以非线性方式影响T,可将二者的比例分别控制在5%、17%以内。绿地空间格局对周围温度的影响上,ΔT与核心指标显著正相关,与孤岛、边缘指标显著负相关。ΔT随边缘、分支指标的增加先快速下降后逐渐趋于平稳,需尽可能避免绿地核心斑块被割裂与出现分支。环线仍以非线性方式影响ΔT,适宜控制其比例在6%。

The Influence of Urban Green Spaces on Thermal Environment Based on Morphological Spatial Pattern Analysis

Urban green space plays a significant role in improving the thermal environment.Previous studies have focused on the relationships between the thermal environment and the spatial pattern of green space.However,less attention is devoted to the influence of green space's inner structure on the thermal environment and implications for green space planning and design.In this paper,we use seven indices to quantify the spatial pattern of green space through morphological spatial pattern analysis(MSPA).Twenty-five green space areas in Wuhan's central city are selected to investigate the spatial pattern's effects on the mean temperature inside green space(T)and the cooling range(ΔT)concerning the point-surface,boundary,and corridor of green space.Landsat 8 remote sensing data are used to calculate the land surface temperature.We report three principal results.First,the twenty-five green space areas are classified into four types:(1)Significant internal and external cooling;(2)Significant internal cooling;(3)Moderate cooling;And(4)little cooling.The difference of MSPA indices among these four types of green space is found predominantly in the core,islet,and branch.Second,T is significantly negatively correlated with the core_per and perforation_per but positively correlated with the islet_per and branch_per.Possible strategies to improve the cooling effect of green space include strengthening the integration of green space,enhancing the core green patches’internal boundary,decreasing the number of small fragmented patches,and avoiding corridors connecting to only one side of the core patches.The loop_per and branch_per affect T in a nonlinear way,and the proportions of them would be controlled within 5%and 17%,respectively.Third,ΔT is significantly positively correlated with the core_per and negatively correlated with the islet_per and edge_per.ΔT decreases rapidly as the edge and branch_per increase and then levels off.It is critical to avoid splitting the core green patches and the development of branches.The loop affectsΔT in a nonlinear way,with an appropriate proportion of 6%.