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Cooling is an important ecosystem service of street greenery. This study explores the local/micro scale relationship between street greenery and daytime air temperature in street canyons in Birmingham, UK. It analyses, for a range of atmospheric stabilities, the correlation between air temperature and indexes obtained from open-source street-level images (Google Street View) through semantic segmentation as parameters for street greenery quantity. Results show that under ideal conditions without the effects of buildings' shading, street greenery is most likely to have a significant correlation with air temperature when atmospheric stability is high with shading from tree canopies appearing to be the main greening factor in promoting cooling. However, the study also shows the importance of other non-greening factors, such as the position of people relative to the tree canopy and the sun, as well as the shade provided by buildings along streets. Overall, this study provides new insights into the nature of the relationship between urban greenery and meteorology and shows the value of using street view data for evaluating the cooling benefits of greenery. For practitioners, it demonstrates the importance of understanding the local conditions when using urban greenery for heat mitigation. • Street greenery's cooling effect is positively related to atmospheric stability. • Shading of tree canopy is the primary mechanism of street greenery's cooling effect. • Buildings along streets may influence the cooling effect of street greenery. • Street view images have potential in assessing street greenery's cooling effect.
Lu et al. (Sat,) studied this question.