The Cooling Effect of Urban Green Spaces in Metacities: A Case Study of Beijing, China’s Capital

Liang Yan,Shuqing Zhao,Wenxiao Jia

doi:10.3390/rs13224601

Abstract

Urban green spaces have many vital ecosystem services such as air cleaning, noise reduction, and carbon sequestration. Amid these great benefits from urban green spaces, the cooling effects via shading and evapotranspiration can mitigate the urban heat island effect. The impact of urban green spaces (UGSs) on the urban thermal environment in Beijing was quantified as a case study of metacities using four metrics: Land surface temperature (LST), cooling intensity, cooling extent, and cooling lapse. Three hundred and sixteen urban green spaces were extracted within the 4th ring road of Beijing from SPOT 6 satellite imagery and retrieved LST from Landsat 8 remote sensing data. The results showed that the cooling intensity of green spaces was generally more prominent in the areas with denser human activities and higher LST in this metacity. Vegetation density is always the dominant driver for the cooling effect indicated by all of the metrics. Furthermore, the results showed that those dispersive green spaces smaller than 9 ha, which are closely linked to the health and well-being of citizens, can possess about 6 °C of cooling effect variability, suggesting a great potential of managing the layout of small UGSs. In addition, the water nearby could be introduced to couple with the green and blue space for the promotion of cooling and enhancement of thermal comfort for tourists and residents. As the severe urban heating threatens human health and well-being in metacities, our findings may provide solutions for the mitigation of both the urban heat island and global climate warming of the UGS area customized cooling service.

Highlights

Urban green spaces (UGSs) provide various environmental, ecological, and social benefits to urban communities [1] such as beautifying landscape, freshening air [2], improving urban climate [3], mitigating urban carbon emissions [4], harboring biodiversity [5], boosting social and cultural cohesion [6], etc
Three metrics of UGSs’ cooling effect were shown in Figure 3b–d: UGSs’ cooling extent (CE) averaged at 100.0 ± 74.4 m, with a maximum value of 474.0 m; cooling intensity (CI)
The impact of 316 UGSs on the urban thermal environment in Beijing is quantified as four metrics: land surface temperature (LST), CI, CE, and cooling lapse (CL) with SPOT 6 and Landsat images

Summary

Introduction

Urban green spaces (UGSs) provide various environmental, ecological, and social benefits to urban communities [1] such as beautifying landscape, freshening air [2], improving urban climate [3], mitigating urban carbon emissions [4], harboring biodiversity [5], boosting social and cultural cohesion [6], etc. Amid these great benefits from UGSs, the cooling effects have received increasing attention in an increasingly warming urban environment, especially in cities with highly-dense residents [7,8,9]. Remote sensing data have confirmed the existence of the cooling effect on land surface temperature (LST) on a larger

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