Recent Decelerating Trends of Urban Warming in Japan

Temperature trends in Japanese cities were analyzed using data at 433 stations on the AMeDAS network from April 1979 to March 2023. It was found that urban warming, defined by a temperature increase at an urban station relative to the surrounding non-urban stations, had slowed down in the latter part of the analysis period. The deceleration of urban warming was commonly found for northern, eastern, and western Japan, and not only for stations in densely inhabited areas but also those at weakly urbanized sites where the surrounding population density was 100-300 km⁻². The deceleration was observed in all seasons and time of the day, although it tended to be more conspicuous in winter than in other seasons, and in the nighttime than in the daytime.