Determining Favourable and Unfavourable Thermal Areas in Seoul Using In-Situ Measurements: A Preliminary Step towards Developing a Smart City

Abstract

Urban heat island effects (UHIE) are becoming increasingly widespread, thus, there is an urgent need to address thermal comfort, which significantly influences the daily lives of people. In this study, a means of improving the thermal environment by spatial analysis of heat was implemented to ensure basic thermal comfort in future smart cities. Using Seoul as the study site, the relationship between sensible heat and land cover type was used to identify heat islands in this city. Thereafter, k-means clustering was employed to extract unfavourable and favourable thermal areas. High sensible heat indicates locations where environmental heat needs to be mitigated. Sensible heat distribution data were used for spatial typification to formulate an effective land cover factor to mitigate the UHIE. In-situ net radiation data measured at six sites were utilised to confirm the spatial typification of the thermal environment. It was found that expanding the green space by 1% reduces the sensible heat by 4.9 W/m2. Further, the building coverage ratio and green coverage influence the sensible heat in compact residential areas. The study results can be used to establish spatial planning standards to improve the thermal environments of sustainable cities.

Is Sensible Heat Flux Useful for the Assessment of Thermal Vulnerability in Seoul (Korea)?

“…In the second part, we estimated the sensible heat flux in community scale (Equations (3), (A1)-(A4), Tables A1 and A2) for the comparison in the first part. In this step, we rasterised the sensible heat flux based on existing data (Appendices A and B), considering the energy balance, net radiation, latent heat, sensible heat, storage heat, and artificial heat [24]. Then, we used the heat flux as a variable of sensible heat vulnerability.…”

“…Data were constructed from equipment installed at least 15 m above the ground (i.e., four stories). Sensible heat flux was calculated using the energy budget model adopted from previous studies [24]. The value was calculated using a thermodynamic model that considers the urban canyon structure.…”

“…Sensible heat flux was derived based on four types of heat flux [24]. We used the following energy budget model to calculate sensible heat flux based on net radiation (Q n ), which was derived by Offerle [89].…”

“…Low vulnerability values in the city's core district may have been influenced by high building density or high income, as high-rise buildings exert a cooling effect by providing shade. In some cases, cooling is associated with high plant density and the presence of green infrastructure, parks, or other green areas [24,93]. In other cases, lower levels of impervious surfaces are associated with lower temperatures and reduced thermal vulnerability.…”

“…Thermal vulnerability has been popularly assessed by heat events based on summer temperature [21,23]. Since temperature is the result of heat exchange, we need to understand the mechanism of space and heat flux to find adaptation methods in thermally vulnerable areas [24]. The aim of this study was to compare whether sensible heat flux, which is more effective than temperature in quantitative thermal environment analysis [25,26], is more effective than temperature in vulnerability assessment.…”