Comparative study of summer heat reduction measures in the city of Jeju, Republic of Korea

Due to the effects of climate change, summer heat waves are getting hotter and longer. Urban spaces show a stronger heat island effect due to the effects of artificial structures such as three-dimensional buildings and impervious pavements. This study aimed to compare various methods of improving the summer heat environment in urban spaces in Jeju, Republic of Korea, at four locations (sunny, street trees, artificial shading device, and mist spray). Microclimate data (air temperature, relative humidity, wind speed and direction, and short- and long-wave radiation) were measured from 12:00 to 16:00, which is the mist spraying operation time on July 31 and August 1, 2024, at a height of 1.2 m above the ground per minute. The physiological equivalent temperature (PET) and universal thermal climate index (UTCI) were calculated using microclimate data measured at the four locations. In the PET, the points under the shade of street trees, the artificial shading device, and the mist spray were 11.1-12.4°C, 7.5-8.7°C, and 0.5-0.9°C lower on average than the sunny point, respectively, showing thermal perception reduction effects of 1.8-2, 1.2-1.5, and 0.1-0.2 levels. In the UTCI, the three points above were 6.1-7.1°C, 3.8-5.1°C, and 0.7-1.1°C lower on average, respectively, showing heat stress reduction effects of 1.0-1.2, 0.6-0.8, and 0.1-0.2 levels. Among the methods for improving the thermal environment in summer, the street trees had the highest effect, and the artificial shading device showed a heat reduction effect that was a 1/2 level lower than the street trees. The mist spray was shown to have a weak heat reduction effect, but the Jeju research site was sprayed from the bottom up, so it may have been different from spraying from above. More international research should be conducted on ways to improve the heat environment during the summer season.