日本ヒートアイランド学会

西村香純 Kazumi Nishimura *1
三坂育正 Ikusei Misaka *2
加藤太朗 Taro Kato *1
宮田聡 Satoshi Miyata*1
新居久朋 Hisatomo Arai *1
上園慎哉 Shinya Uezono *1
高野了成 Ryousei Takano *1 

*1 産業技術総合研究所  National Institute of Advanced Industrial Science and Technology
*2 武蔵野大学 Musashino University 

概要

This study developed and validated a CFD simulation model for assessing heat stress in an urban environment, focusing on the Nishi-Shinjuku district of Tokyo. A high-resolution simulation was conducted by setting up a computational domain based on the PLATEAU 3D urban model and applying observed meteorological and radiative conditions. In parallel, field measurements were carried out on the same day and at the same time to obtain Wet-Bulb Globe Temperature (WBGT) and its components—dry-bulb temperature, wet-bulb temperature, and globe temperature—for detailed comparison with the simulation results. The analysis revealed that prediction errors varied depending on location and time, with a tendency toward overestimation during peak solar radiation periods. A component-wise error analysis showed that globe temperature contributed most significantly to WBGT prediction errors, followed by wet-bulb temperature, which exhibited high sensitivity. These errors were attributed to multiple factors, including the representation of solar shading, surface radiative properties, and wind fields, and were influenced by simplifications in the modeling process. The findings highlight the importance of accurately modeling radiative environments and applying high-resolution meteorological boundary conditions to improve WBGT prediction accuracy in urban areas. 

横山 仁　Hitoshi YOKOYAMA*1 長谷川 薫　Kaoru HASEGAWA*1,2 日下 博幸　Hiroyuki KUSAKA*3 　

*1 防災科学技術研究所 National Research Institute for Earth Science and Disaster Resilience

*2 現所属 ESRI ジャパン株式会社 Esri Japan Corporation

*3 筑波大学計算科学研究センター Center for Computational Sciences, University of Tsukuba

概要

We installed thermometers in instrument shelters at elementary schools in Tsukuba City, Ibaraki Prefecture, and conducted mobile observations using a car to investigate nighttime air temperature distribution in the city. Nighttime air temperatures were high in Kasuga and Midori-no-chuo districts, and low in Yoshinuma district. These results differed from the 2008 observations by Kusaka et al. (2012), who reported that the highest air temperatures were near Tsukuba Station. When we investigated the relationship between nighttime temperatures and green coverage ratio of the area, we found higher negative correlation (R=-0.67), meaning that even in the city center, air temperature was lower if green coverage ratio was higher. Since nighttime air temperatures are said to be closely related to heatstroke and sleep disorders, it is also important for Tsukuba City to maintain and increase green coverage ratio.