Extreme heat is Australia’s most perilous natural hazard, and increasing urban temperatures due to climate change are a growing concern. Consequently, there is growing interest in developing nature-based solutions (i.e., greenery and vegetated surfaces) to cool urban areas. Appropriately designed urban parks are anticipated to be crucial for maintaining thermal comfort as temperatures rise. The two main diurnal cooling mechanisms of urban parks are shade provision and vegetation transpiration. However, limited studies have examined the cooling performance of vegetation through transpiration, especially in the southern hemisphere. This study addresses this gap by examining the microclimatic conditions, cooling benefits, and thermal performance of a typical neighbourhood park in Perth, Western Australia, with a focus on the cooling performance of vegetation through shade and transpiration. Present and future microclimates were modelled and simulated for average and hottest summer days based on 25 years of local weather data and projections for 2090 under the Representative Concentration Pathway (RCP) 8.5 scenario. The findings reveal that trees provided diurnal cooling benefits for park users by lowering the Universal Thermal Comfort Index (UTCI) by up to 17°C, with this benefit persisting in projected 2090 conditions. This cooling benefit was predominantly achieved through shade provision, with marginal contributions from transpiration. Additionally, on hot days, as leaf temperature exceeded 30°C, increased stomatal resistance led to reduced transpiration. Therefore, more attention must be paid to transpiration cooling limits due to stomatal closure during hot hours to improve cooling performance in park design. Moreover, comparing different plant species’ behaviour and adaptability on hot days is crucial, especially in future climatic conditions.

中文翻译：

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当前和未来气候情景下的公园热舒适和冷却机制


极端高温是澳大利亚最危险的自然灾害，气候变化导致的城市气温升高越来越令人担忧。因此，人们对开发基于自然的解决方案（即绿色植物和植被表面）来为城市地区降温的兴趣越来越大。预计设计合理的城市公园对于在气温升高时保持热舒适性至关重要。城市公园的两个主要昼夜降温机制是遮荫和植被蒸腾。然而，有限的研究通过蒸腾作用检查了植被的冷却性能，尤其是在南半球。本研究通过检查西澳大利亚珀斯一个典型社区公园的小气候条件、降温效益和热性能来解决这一差距，重点是植被通过遮荫和蒸腾作用的降温性能。根据 25 年的当地天气数据和在代表性浓度路径 （RCP） 8.5 情景下对 2090 年的预测，对平均和最热的夏季进行了建模和模拟，模拟了现在和未来的小气候。研究结果表明，树木通过将通用热舒适指数 （UTCI） 降低高达 17°C 为公园使用者提供了昼夜降温的好处，这种好处在预计的 2090 年条件下仍然存在。这种降温效益主要是通过提供阴凉处来实现的，蒸腾作用的贡献很小。此外，在炎热的天气里，当叶温超过 30°C 时，气孔阻力增加导致蒸腾作用减少。因此，必须更加注意由于炎热时段气孔关闭而导致的蒸腾冷却限制，以提高公园设计的冷却性能。 此外，比较不同植物物种在炎热天气下的行为和适应性至关重要，尤其是在未来的气候条件下。