In high-density urban areas, pocket parks offer significant potential to mitigate thermal discomfort. However, the specific contributions of horizontal and vertical canopy structures to pocket parks’ cooling and thermal comfort effects remain unclear. This study addresses this gap by selecting 14 typical pocket parks in Shanghai and collecting high-resolution canopy and thermal data using unmanned aerial vehicles (UAVs). Generalized additive models were applied to assess the relationships between thermal conditions and spatial variables. The cooling effects were quantified by comparing the relative differences in surface temperature (Ts) and air temperature (Ta) between the pocket parks and non-vegetated reference sites, while thermal comfort was assessed using the Universal Thermal Climate Index (UTCI). The results revealed that: (1) On average, Ts was 3.98 °C lower, Ta was 1.18 °C lower, and UTCI was 3.74 °C lower in pocket parks than in non-vegetated sites. (2) A positive linear relationship was found between ΔUTCI and canopy coverage, indicating that increased canopy coverage enhances thermal comfort. (3) When considering three-dimensional (3D) metrics, mean foliage height was positively correlated with both ΔTa and ΔUTCI, while foliage height diversity had a negative impact. Notably, the ΔUTCI decreased when the 3D green volume exceeded 22 m3, suggesting that parks with tall, single-layer canopies composed of multiple small trees, each with a 3D green volume below 22 m3, optimize thermal benefits in summer. This study provides critical insights into the cooling and thermal comfort effects of pocket parks, offering practical guidance for park maintenance and redesign, particularly in the context of urban heat mitigation and adaptation strategies.

中文翻译：

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在炎热的夏日，垂直雨棚结构为城市袖珍公园提供凉爽和热舒适性


在高密度的城市地区，袖珍公园在缓解热不适方面具有巨大潜力。然而，水平和垂直冠层结构对袖珍公园的冷却和热舒适效果的具体贡献仍不清楚。本研究通过选择上海的 14 个典型袖珍公园并使用无人机 （UAV） 收集高分辨率树冠和热数据来解决这一差距。应用广义加法模型来评估热条件和空间变量之间的关系。通过比较袖珍公园和非植被参考地点之间表面温度 （Ts） 和空气温度 （Ta） 的相对差异来量化冷却效果，同时使用通用热气候指数 （UTCI） 评估热舒适度。结果表明：（1） 与无植被地点相比，袖珍公园的 Ts 平均低 3.98 °C，Ta 低 1.18 °C，UTCI 低 3.74 °C。（2） ΔUTCI 与冠层覆盖率呈正线性关系，表明冠层覆盖率增加增强了热舒适性。（3） 在考虑三维 （3D） 指标时，平均叶高与 ΔTa 和 ΔUTCI 呈正相关，而叶高多样性具有负向影响。值得注意的是，当 3D 绿化体积超过 22 m3 时，ΔUTCI 降低，这表明公园拥有由多棵小树组成的高大单层树冠，每棵小树的 3D 绿化体积低于 22 m3，在夏季的热效益最佳。本研究为袖珍公园的冷却和热舒适效应提供了重要见解，为公园维护和重新设计提供了实用指导，尤其是在城市热缓解和适应策略的背景下。