The relationship between street greenery and daytime air temperature: a study based on parameters derived from street view images

Street greenery can reduce the air temperature in street canyons, thus regulating the urban microclimate and improving the thermal comfort of pedestrians and residents. Assessing and predicting this cooling effect can assist in the rational planning of green infrastructure. This study introduces the parameters derived from open-source street-level images (Google Street View) and obtained by semantic segmentation based on deep learning as a quantitative indicator of street greenery. This approach has multiple advantages compared with traditional urban greenery auditing methods. This study chooses two roads in Birmingham, UK, as study sites. While collecting greenery parameters on these roads, this study recorded air temperature in those street canyons during a heatwave period in the summer of 2023. and explored the links between greenery and air temperature by correlation analysis. The association between street-view-derived greenery parameters and air temperature under clear summer weather conditions has been proved. Furthermore, this study indicated that shading by street tree canopies is the major mechanism for the cooling benefit of street greenery. Therefore, the location of tree canopies and the shade provided by buildings along street canyons may also affect the intensity of the cooling effect of street greenery. This study can be further used to assess, map, and predict the cooling effect of street greenery at the city level and assist in the planning of street greenery to maximize its cooling benefits.