Influence of urban surface compositions on outdoor thermal environmental parameters on an urban road: A combined two-aspect analysis

The summer outdoor thermal environment is gradually deteriorating in most cities in low and middle latitudes under global warming, threatening human health and life. This study was conducted to improve this situation, in which urban surface compositions were seen as the main influencing factors at vertical and horizontal levels. Results showed urban surface compositions affected the outdoor thermal environment at both levels. CVI and GVI were the key vertical factors, while NDBI and NDVI were the crucial horizontal ones. More importantly, synergies on the outdoor thermal environment between the two levels were found, and they were higher than any single level; the sums of the independent effects were 27.05% and 64.21%, and the synergetic explanatory powers were 9.10% and 34.37% for air temperature and humidity, respectively. The potential reason for the synergy between the two levels was attributed to their correlation, especially for the CVI and GVI to the NDBI and NDVI. The TVoEs of the CVI and GVI were 0.31 and 0.17, respectively, regulating air temperature at the vertical level, and the TVoE of the NDVI was 0.33, coordinating humidity at the horizontal level. These results provide scientific evidence and data support for urban planning and landscape design.