How can green spaces smaller than 1 ha improve outdoor thermal conditions in urban neighbourhoods? Considering the variability of cooling effects based on the relevant urban design parameters of size, shape, and spatial distribution, this study entailed development of different design scenarios combining these parameters for four neighbourhood typologies and simulates the thermal sensation of these scenarios using ENVI-met. Three aspects of cooling effects — the inside and outside cooling as well as the Park Cool Island (PCI) effects of the green spaces are separately analysed. The study shows that inside the small green spaces, the mean Physiological Equivalent Temperature (PET) of different cases can vary up to 4 ℃. Larger green spaces with a squared shape lead to cooler PET inside. For a good cooling outside the green spaces, a configuration of grouped small green areas can reduce the PET by 1.3 ℃, with distribution of the green spaces being the most influential factor. The PCI effect is mainly determined by size and shape of the green spaces, where a bigger size and squared shape leads to better cooling effects. But for neighbourhoods with radial streets, it is more related to the spatial distribution, which can result in a reduction of 10.2 ℃ in PCI for linear green spaces next to narrow streets. Guidelines for effective design scenarios are generated from this research, providing urban designers and planners with practical reference in neighbourhood greening projects for cooler cities.

中文翻译：

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小型绿地如何为城市社区降温：优化分布、大小和形状


小于 1 公顷的绿地如何改善城市社区的室外热能条件？考虑到基于规模、形状和空间分布等相关城市设计参数的冷却效果的可变性，本研究需要开发不同的设计方案，将这些参数组合成四种社区类型，并使用 ENVI-met 模拟这些方案的热感觉。分别分析了冷却效果的三个方面 — 内部和外部冷却以及绿地的公园凉爽岛 （PCI） 效果。研究表明，在狭小的绿色空间内，不同情况的平均生理等效温度 （PET） 变化可达 4 °C。较大的方形绿地会导致 PET 内部温度较低。为了在绿地外进行良好的冷却，分组的小绿地配置可以将 PET 降低 1.3 °C，其中绿地的分布是影响最大的因素。PCI 效果主要由绿地的大小和形状决定，其中较大的尺寸和方形形状会带来更好的冷却效果。但对于具有放射状街道的社区，它与空间分布更相关，这可能导致狭窄街道旁边的线性绿地的 PCI 降低 10.2 °C。这项研究产生了有效设计方案的指南，为城市设计师和规划师在较冷城市的社区绿化项目中提供了实际参考。