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

Abstract

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.

Keywords: health; heat vulnerability index; heat-related mortality rate; sensible heat flux; sensible heat vulnerability; thermal comfort and health; thermal environment; urban heat island effect.

Figure A1

Input data: (a) impervious surfaces; (b) green spaces; (c) buildings; (d) water and wetlands; (e) roads; and (f) administrative map.

Figure A2

Calinski-Harabasz (C-H) Index Analysis for the level range of vulnerability.

Figure A3

Street views of top three-ranked and bottom three-ranked communities for thermal sensitivity.

Figure A4

Street views of top three-ranked and bottom three-ranked communities for thermal adaptive capacity.

Figure A5

Street views of top three-ranked and bottom three-ranked communities for climate exposure.

Figure 1

Map of Seoul. Note: CBD refers to a traditional business district. YBD indicates Yeoido business district, and GBD stands for Gangnam business district. These three districts are the main urban centres in Seoul [77]. The variable “admin_GU” represents 25 administrative districts and “ADMIN_DONG” refers to neighbourhood administrative districts. Source: GIS map (https://sgis.kostat.go.kr).

Figure 2

Flow chart of research methods.

Figure 3

Three indices of temperature and sensible heat flux. Note: (a) Sensitivity to both temperature and sensible heat; (b) Adaptive capacity to both temperature and heat; (c) Exposure to temperature; (d) Exposure to sensible heat; Standardised value class (range): 1 (0~0.20), 2 (0.21~0.40), 3 (0.41~0.609), 4 (0.61~0.80), 5 (0.81~1.00).

Figure 4

Mortality rate in relation to vulnerability based on temperature and sensible heat flux. Note: Vul_temp (red): temperature vulnerability (vulnerability based on temperature); Vul_heat (black): sensible heat vulnerability (vulnerability based on sensible heat flux).

Figure 5

Vulnerability to heat flux and temperature in relation to mortality rate. (a) Temperature Vulnerability index; (b) Sensible heat vulnerability index; (c) Heat-related illness mortality rate. Note: Clustering Class (range): 1 (0~0.08), 2 (0.08~0.32), 3 (0.32~0.49), 4 (0.49~0.76), 5 (0.76~1.00). Because there are none values ( = 0) on mortality rate in communities, the range of the both sensible heat and temperature vulnerability was classified using hierarchical clustering to compare with the death rate.

Figure 6

Street views of the relative highest and lowest sensible heat vulnerability. Note: Twelve street views for six communities representing the highest rank (the first through the third picture ①~⑥) and the lowest rank (436th through 438th, picture ⑦~⑫), each of which can relate its context and situation to the community’s thermal vulnerabilities.