2025 Reports

Long-Term Variation of Urban Heat Island Intensity Over the Past Half-Century in Seoul, Korea

Hong, Jinkyu; Hong, Je-Woo

Urban heat island (UHI), a consequence of anthropogenic activities and climate conditions, affects air pollution, energy use, and health. Therefore, a better understanding of the temporal dynamics of UHI is required for sustainable urban planning to mitigate air pollution under a changing climate. Here, we present the evolution of UHI intensity (UHIi) and its controlling factors in the Seoul metropolitan area, Korea, over the last 56 years (1962–2017), which has experienced unique compressed economic growth and urban transformation under a monsoon climate. The analysis demonstrated an inverted U-shape long-term variation of UHIi with the progress of urban transformation and economic climate, which has not been reported in Asian cities before. Meanwhile, short-term variations in UHIi are related to both diurnal temperature range and duration after rainfall events, unlike previous studies, and the UHIi was exacerbated by heat waves. Our findings suggest that the UHIi will exhibit different temporal dynamics with future changes in the monsoon climate, and heat waves in the urban area will be reinforced if current rapid urbanization continues without a shift toward sustainable and equitable development. Asian cities expected to undergo similar patterns of urbanization should ensure that their (re)development strategies account for changes in rainfall intensity and timing caused by variations in the monsoon system under a changing climate. Additionally, these strategies should include measures to mitigate the combined effects of heat waves and the urban heat island (UHI) phenomenon.