Is shading a better way to cool down? Evaluation and comparison of the cooling capacity of blue-green spaces and urban shade

Abstract

The issue of cooling cities has emerged as a significant global urban planning strategy to address the challenges posed by extreme heatwaves. Scholars have conducted extensive research on the most effective methods for reducing surface temperature at the city scale. Blue-green infrastructure has emerged as a key cooling factor in high-density cities. However, on-site measurements have indicated that the cooling effect of shade can be even stronger than the transpiration effect of green plants. Nevertheless, there is still a paucity of empirical research on the cooling effect of shade at the city scale. This article employs the Urban Multi-scale Environmental Predictor (UMEP) tool to simulate the spatio-temporal patterns of urban shade on Xiamen Island. This is done to ascertain the cooling effect of shade in comparison with other cooling factors, including green space, water bodies, and building height. The results indicate that: 1) The shade profiles of Xiamen Island show a “high-low-high” pattern throughout the day, with trees being the main source of shade. 2) Overall, the cooling effect of shading is more pronounced than other factors for most of the day time, but due to its ineffectiveness in cooling internally released heat, the cooling effect of shading decreases significantly at dusk, although the shading pattern is similar to that in the morning. 3) The area in which shading exerts a cooling influence is more extensive than other factors throughout the daylight hours. These effects are concentrated in the south, west and north, but at dusk, they become a warming influence in the east. This paper serves as an effective reference for future heat adaptation planning.

Keywords

• Building and Tree Shadows
• Land Surface Temperature
• Cooling Effect
• UMEP
• GWR