Developing a three-dimensional urban surface model for spatiotemporal analysis of thermal comfort with respect to street direction

Understanding the urban heat problem, which is intensifying owing to urbanization and climate change, has become a great challenge. Evaluating the thermal environment of urban spaces and predicting changes based on urban planning are essential for developing optimal urban cooling plans. This study addresses the pressing challenge of urban heat by developing a three-dimensional urban surface model (3D-USM) and conducting spatiotemporal thermal comfort simulations, providing valuable insights for the development of effective urban cooling strategies in the face of urbanization and climate change. Mean radiant temperature (MRT), the key element of thermal comfort of humans by reflecting complex urban environments was simulated in east-west streets which are vulnerable to heat, and results demonstrate that a small change of street angle has a significant effect on pedestrian thermal comfort. Specifically, at 0900 LST, the southern sidewalk of the street rotated by 12.5° was more vulnerable than the northern sidewalk. This resulted in a shift in the optimal location of trees that provide effective cooling, highlighting the importance of considering street orientation in the placement of urban greenery. This suggest that spatiotemporal thermal comfort simulations considering urban form in detail are necessary to efficiently cool the city. The proposed 3D-USM, capable of accurately and efficiently simulating the thermal environment and MRT thermal comfort in complex urban environments using simple input data, holds great potential for guiding the development of efficient cooling strategies to foster sustainable cities.