Shading is one of the most effective strategies to mitigate urban local-scale heat stress during summer. Therefore, this study investigates the effects of shading caused by buildings and trees via exhaustive field measurement research on urban outdoor 3D radiant environment and human thermal comfort. We analyzed the characteristics of micrometeorology and human thermal comfort at shaded areas, and compared the difference between building and tree shading effects as well as that between shaded and sunlit sites. The results demonstrate that mean radiant temperature T_mrt (mean reduction values of 28.1°C for tree shading and 28.8°C for building shading) decreased considerably more than air temperature T_a (mean reduction values of 1.9°C for tree shading and 1.2°C for building shading) owing to shading; furthermore, the reduction effect of shading on UTCI synthesized the variation in the above two parameters. Within the shaded areas, short-wave radiant components (mean standardized values of 0.104 for tree shading and 0.087 for building shading) decreased considerably more than long-wave radiant components (mean standardized values of 0.848 for tree shading and 0.851 for building shading) owing to shading; the proportion of long-wave radiant flux densities absorbed by the reference standing person was high, leading to a relatively high long-wave mean radiant temperature, and R² between long-wave mean radiant temperature and air temperature exceeded 0.8. Moreover, the directional sky view factor (SVF) was utilized in this study, and it showed significant positive correlation with short-wave radiant flux densities, but no statistically evident correlation with long-wave radiant flux densities. Meanwhile, T_mrt was most relevant with SVF_S⟶ with R² of 0.9756. Furthermore, UTCI rose two categories at the sunlit areas compared with that at the shaded areas. In contrast, T_a and T_mrt played the first positive role in UTCI at shaded and sunlit areas, respectively.

中文翻译：

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东北城市居住区附近建筑物和树木遮荫对夏季3D辐射环境和人体热舒适性的现场评估

遮阳是缓解夏季局部城市高温压力的最有效策略之一。因此，本研究通过详尽的现场测量研究来研究建筑物和树木造成的阴影对城市室外3D辐射环境和人体热舒适性的影响。我们分析了阴影区域的微气象学特征和人体热舒适性，并比较了建筑物和树木的阴影效果以及阴影和阳光照射位置之间的差异。结果表明，平均辐射温度T _mrt（树荫下的平均减少值为28.1°C，建筑物树荫下的平均减少值为28.8°C）比气温T _a降低得更多。（由于遮荫，树木遮荫的平均降低值为1.9°C，建筑物遮蔽的平均降低值为1.2°C）；此外，遮光对UTCI的减少作用综合了上述两个参数的变化。在阴影区域内，短波辐射分量（树影的平均标准值为0.104，建筑树影的平均标准值为0.087）比长波辐射分量（树影的平均标准值为0.848，建筑树影的平均标准值为0.851）下降得更多。遮蔽 参考站立的人吸收的长波辐射通量密度的比例很高，导致相对较高的长波平均辐射温度，R ²长波平均辐射温度与气温之间的关系超过0.8。此外，在这项研究中使用了定向天空视野因子（SVF），它与短波辐射通量密度显示出显着的正相关，但与长波辐射通量密度没有统计上的显着相关。同时，T _mrt与_SVFS⟶最相关，R ²为0.9756。此外，与阴凉处相比，UTCI在日光照射下上升了两类。相比之下，T _a和T _mrt在UTCI中分别在阴影和阳光照射的区域起着第一个积极作用。