Urban Heat Island with Urban Size

    The urban heat island (UHI) effect refers to a phenomenon where certain areas within an urban area exhibit higher temperatures than surrounding suburban areas. Typically, if the temperature difference between an urban area and its suburban counterpart is 2℃ or more over a set period, it is considered a sign of the urban heat island effect. The urban heat island effect arises due to dense urban development, changes in land cover, and the release of anthropogenic heat from buildings and vehicle emissions associated with industrialization and population concentration. It is particularly influenced by the size of the urban population, as well as by land use and the spatial characteristics of the city.

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“This study focuses on the correlation between urban size and the intensity of the urban heat island effect, with the aim of understanding how urbanization impacts atmospheric conditions."

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    The urban heat island effect is more pronounced at night, while the temperature difference between urban and suburban areas is less distinct in the early morning. This is because the urban surface stores heat during the day, gradually releasing it at night. This process, known as a “heatsink”, causes the city to remain warmer than its surroundings at night. These elevated atmospheric temperatures impact not only energy consumption and air quality but also human health and comfort. The urban heat island effect, driven by urbanization, disrupts the inflow of cool, fresh air from surrounding green spaces into urban areas and hinders the dispersion of air pollutants, effectively blocking essential convection processes. The problems caused by the urban heat island effect extend beyond discomfort; for example, the 2003 heatwave in London led to over 600 deaths, highlighting its severe consequences. Seoul also has experienced substantial impacts from the urban heat island effect, with increased mortality and medical visits during extreme heat events. Alarmingly, the mortality rate associated with the urban heat island effect can rise by up to 150% when temperatures reach 36°C compared to 30°C.

    According to Kim(2001), the characteristics of urban heat islands in Korea are changing with climate change. Unlike in other countries, the urban heat island effect in Korea can occur even on cloudy days when solar radiation is partially blocked due to the influence of the hot, humid North Pacific air mass. The intensification of climate change is increasing the frequency of heavy rainfall and causing hot, humid cloudy days to occur more frequently. This hazy, hot, and humid urban heat island effect under restricted solar radiation is more unpleasant than simple heat waves and leads to increased energy consumption and air pollution.

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“Therefore, this study aims to assess the impact of climate change on the urban heat island effect by applying SSP climate change scenarios, and to evaluate the projected outcomes accordingly.”

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