摘要:城市绿地在夏季高温时具有明显降温作用，但在不同地区降温效果及其影响因子存在一定差异。以上海市为例，基于高分影像和实地观测，调查分析了18个典型样地夏季降温效应及其关键影响因子。结果发现：上海城市绿地夏季日均降温1.17-5.60℃，其中67%观测样地降温幅度低于平均值（2.51℃）；绿地降温幅度与对照点的环境温度显著正相关，当外界环境温度低于26℃时，城市绿地降温效应不明显；此外，城市绿地覆被格局对其降温效应有明显影响，当绿地乔木密度增加5%、叶面积指数增大1或者水面比例增加20%时，可使夏季绿地降温率分别提高1.73%、1.66%和1.18%。因此，在全球气候变暖背景下，优化提升上海城市绿地覆被格局可有效提升夏季绿地降温效应。



Abstract:Climate change is one of the most serious challenges in the 21st century. Accompanied by the rapid expansion of cities worldwide, the phenomenon of urban heat islands (UHI) has become a critical environmental issue in many large cities. The health consequences of UHI range from thermal discomfort to life-threatening medical conditions. Fortunately, trees and vegetation in the city can be considered as an ecological measure to cool cities. Although there are numerous studies on microclimate-adjusting effects of urban green spaces, the relationship of landscape pattern of urban green space and air temperature reduction is not fully addressed. In this study, by applying field measurement and high-resolution Google Earth Image, we investigated 18 typical green spaces and observed their role in temperature reduction. The results showed that the green space in Shanghai could reduce summer air temperature by 1.17-5.60℃, and approximately two-third green spaces provided a lower cooling effect than the average temperature reduction (2.51℃). The daily temperature reduction of green space was significantly positively correlated with the external ambient air temperature. However, the cooling effect of urban green space was lower when the ambient air temperature was cooler than 26℃. Tree density, leaf area index (LAI), and waterbody proportion inside the green spaces presented the highest influences on the cooling rate. If there is a 5% increase in tree density, 1 increase in LAI or 20% increase in waterbody percentage, the temperature cooling rate of urban green space would be elevated by 1.73%, 1.66%, and 1.18%, respectively. Therefore, we advised the improvement of the cooling effect of urban green spaces in Shanghai through pattern optimization.





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