Many studies have focused mainly on the thermal and energy performance of VGSs on a building scale; however, littleis known about the cooling effect of VGSs in street canyons and its response to different aspect ratios (building height/street width,H/W). Therefore, a scaled outdoor experiment was conducted to investigate the spatiotemporal variationof the urban wind and thermal environment caused by west-facing vertical greenery systems (VGSs) in street canyonswithH/W= 1 and 2 in the subtropical city of Guangzhou, China. On a typical hot day (26th Oct. 2021), VGSs reducedwind speed by 38.0 % and 21.0 % in street canyons withH/W= 1 and 2, respectively. Compared with the referencecases, the temperature regimes of VGS cases (H/W= 1 and 2), including west-facing wall temperature (Tw-west), east-facing wall temperature (Tw-east), ground temperature (T-g), and air temperature (T-a), were all significantly decreased.Because of the cooling effect of VGSs, the maximum reduction ofT(w-west) in the upper level of street canyons withH/W= 1 and 2 was 20.3 and 16.8 degrees C, respectively. The maximum reduction ofTgin the center of the VGS case withH/W= 2 was 4.6 degrees C, which was more pronounced than in the VGS case withH/W= 1 (1.8 degrees C). The maximum reduc-tion ofTaat the pedestrian level along the central axis of street canyons withH/W= 1 and 2 was 0.8 and 1.6 degrees C,respectively, which was more pronounced than at the upper level. The reduction of Tw-west in the upper level and ofTgandTain the VGS case withH/W= 2 was greater than that in the VGS case withH/W= 1 due to lower windspeed and albedo.
