Urban Thermal Environment and Its Future Change in Central Sapporo: A Case Study on Hot, Clear Days in 2022 and 2024

Urban thermal environments have deteriorated due to global warming and urbanization in recent years. This is expected to become prominent in the near future, even in cities classified under the subarctic climate zone like Sapporo. This study aims to evaluate future thermal environments under progressing urban reconstruction and global warming through thermal environment surveys and numerical modeling in central Sapporo. First, air temperature, humidity, and globe temperature were measured in central Sapporo on two hot and clear days and a hot and partial cloudy day. Field observations were sequentially conducted at four locations in a high‐rise building district, a low‐rise residential area, a park, and a botanical garden, and compared with those at a point fixed during the day. The results showed a clear spatial variation in temperature and humidity within the city center. Moreover, a numerical simulation well reproduced this variation among the observation sites. Another hypothetical simulation was performed with a uniform temperature increase of 2 K on one of the observation dates and full redevelopment to be completed in 2030s. The simulation revealed not only a uniform temperature rising but mitigation of hot environment in areas shaded by newly constructed buildings. Downstream turbulence was found to be reinforced behind the new high‐rise buildings. The wet‐bulb globe temperature assessment suggested that the urban thermal environment in central Sapporo would deteriorate due to global warming and would change the spatial distribution by redevelopment.