Outdoor thermal environment on road and its influencing factors in hot, humid weather: A case study in Xuzhou City, China

Abstract

The outdoor thermal environment is deteriorating with global warming and urban heat island effects and has become a widely studied issue. Fruitful results have been acquired, most of which have been limited to two dimensions, while three-dimensional urban morphology has started to draw attention in recent years due to its higher accuracy. In this study, mobile observations were carried out to research the relationships between road elements and outdoor thermal environmental parameters. Various road elements were presented in a new unified visual index system with three-dimensional features, which were created based on the green view index, including the sky view index (SVI), construction view index (CVI), road and pavement view index (R&PVI), green view index (GVI), human view index (HVI) and vehicle view index (VVI); these indices were categorized into “Sky”, “Land” and “Human”. The outdoor thermal environmental parameters included air temperature (Ta), relative humidity (RH), temperature humidity index (THI) and solar radiation (SR). The results showed that the visual indices were different among various sections over the sampling route, as were the outdoor thermal environmental parameters. The visual indices and outdoor thermal environmental parameters were correlated (P < 0.05), and the correlation probability reached 79.17% along the sampling route. However, these probabilities decreased on separate sections. “Land” was the most important to the Ta, RH and THI at a very local spatial and short temporal scale, while a joint effect between “Sky” and “Land” played a leading role in affecting SR. “Human” influenced these outdoor thermal environmental parameters within limited ranges.