The continued increase in average and extreme temperatures around the globe is expected to strike urban communities more harshly because of the urban heat island (UHI). Devising natural and design-based solutions to stem the rising heat has become an important urban planning issue. Recent studies have examined the impacts of 2D/3D urban land-use structures on land surface temperature (LST), but with little attention to the shades cast by 3D objects, such as buildings and trees. It is, however, known that shades are particularly relevant for controlling summertime temperatures. This study examines the role of urban shades created by trees and buildings, focusing on the effects of shade extent and location on LST mitigation. A realistic 3D digital representation of urban and suburban landscapes, combined with detailed 2D land cover information, is developed. Shadows projected on horizontal and vertical surfaces are obtained through GIS analysis, and then quantified as independent variables explaining LST variations over grids of varying sizes with spatial regression models. The estimation results show that the shades on different 3D surfaces, including building rooftops, sun-facing façades, not-sun-facing façades, and on 2D surfaces including roadways, other paved covers, and grass, have cooling effects of varying impact, showing that shades clearly modify the thermal effects of urban built-up surfaces. Tree canopy volume has distinct effects on LST via evapotranspiration. One of the estimated models is used, after validation, to simulate the LST impacts of neighborhood scenarios involving additional greening. The findings illustrate how urban planners can use the proposed methodology to design 3D land-use solutions for effective heat mitigation.

由于城市热岛（UHI），预计全球平均温度和极端温度的持续升高将对城市社区造成更大的打击。设计基于自然和基于设计的解决方案以阻止不断上升的热量已成为重要的城市规划问题。最近的研究检查了2D / 3D城市土地利用结构对地表温度（LST）的影响，但很少注意3D对象（例如建筑物和树木）所投射的阴影。然而，已知阴影对于控制夏季温度特别重要。这项研究考察了树木和建筑物产生的城市阴影的作用，重点是阴影范围和位置对减轻LST的影响。逼真的3D数字表示的城市和郊区景观，再加上详细的2D土地覆盖信息，被开发。通过GIS分析获得投影在水平和垂直表面上的阴影，然后将其量化为自变量，以空间回归模型解释LST在尺寸变化的网格上的变化。估计结果表明，不同3D表面（包括建筑物屋顶，朝阳立面，非朝阳立面）以及2D表面（包括道路，其他铺砌的覆盖物和草皮）上的阴影具有不同影响的冷却效果，表明阴影明显地改变了城市建筑表面的热效应。树木冠层的体积通过蒸散对LST具有明显的影响。验证后，使用其中一种估计的模型来模拟涉及额外绿化的邻里场景的LST影响。