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.

Large cities with a high concentration of high-rise buildings are shaded by urban canyon. This brings a cooling effect compared to the space exposed to the sun, but is not always cool due to the longwave radiation emitted from buildings and the built environment. We tested the micro-scale effects of major external spatial factors, trees, and buildings, under shade on longwave radiation shifts to understand the effects of large shaded areas in megacities. Incoming and outgoing longwave radiations (ILR and OLR, respectively) were found to decrease the overall observation by time zone. Longwave radiation on a micro-scale was also inversely proportional to the tree volume. From mean radiant temperature (MRT) analysis, we found that about a 10% decrease in MRT could be achieved by increasing tree volume by around 50%. Larger tree volumes corresponded to greater blocking effects on longwave radiation. Considering the tree volume, a multilayer urban tree canopy composition can more favorably improve the thermal environment and energy sustainability of a city compared to a single-layer canopy. Larger trees planted with harmonious shrubs are the most effective in reducing longwave radiation.

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Climate change has led to increases in global temperatures, raising concerns regarding the threat of lethal heat waves and deterioration of the thermal environment. In the present study, we adopted two methods for spatial modelling of the thermal environment based on sensible heat and temperature. A vulnerability map reflecting daytime temperature was derived to plot thermal vulnerability based on sensible heat and climate change exposure factors. The correlation (0.73) between spatial distribution of sensible heat vulnerability and mortality rate was significantly greater than that (0.30) between the spatial distribution of temperature vulnerability and mortality rate. These findings indicate that deriving thermally vulnerable areas based on sensible heat are more objective than thermally vulnerable areas based on existing temperatures. Our findings support the notion that the distribution of sensible heat vulnerability at the community level is useful for evaluating the thermal environment in specific neighbourhoods. Thus, our results may aid in establishing spatial planning standards to improve environmental sustainability in a metropolitan community.