Assessment of summer thermal environment and greening effects in Fukuyama Station Square: proposal for square reorganization considering thermal environment improvement

Recently, the summer environment in Japanese cities has been changing, with extreme heat occurring every year due to the urban heat island phenomenon and global warming. Currently, the issue of heat affects everyone, so measures to counteract the urban warming effect are necessary to create safe and comfortable environments in many Japanese cities, including not only large cities but also regional cities. Urban reorganization projects involving the relocation of buildings and the reorganization of urban structures are progressing across Japan and introducing diverse urban designs to mitigate thermal environments during this opportunity is considered an effective measure. Against this background, this study aims to clarify methods for urban development that improve summer thermal environments in the Fukuyama Station Square, where reorganization is planned. In this study, short-term field measurements were conducted to characterize wind conditions and the thermal environment during selected clear summer days. In addition, numerical simulations were performed to estimate the effects of greening under specific hot summer conditions at the target square. For the simulations, we used the Multi-scale Simulator for the Geoenvironment, which can calculate detailed thermal environments on the Earth Simulator. The results confirmed the influence of strong downdrafts generated along high-rise buildings, the cooling effects of large-scale greening within the square, and the contributions of shading from trees and buildings to improved thermal comfort. Based on these findings, square reorganization strategies considering thermal environment mitigation in this area were discussed.