Cool-roof effects on thermal and wind environments during heat waves: A case modeling study in Seoul, South Korea

This study examines cool-roof effects on thermal and wind environments in Seoul, South Korea during the 2018 heat wave through Weather Research and Forecasting (WRF) model simulations. Two 37-day simulations, one with cool roofs that have a higher albedo and the other with conventional roofs, are conducted. In the daytime, cool roofs decrease the 2-m temperature, 10-m wind speed, surface sensible and latent heat fluxes, and planetary boundary layer height but increase the 2-m water vapor mixing ratio. The daytime maximum decreases are 1.0 degrees C in 2-m temperature and 0.5 m s-1 in 10-m wind speed. The cool roof-induced reduction of nearsurface temperature tends to decrease with increasing heat wave intensity. The decrease in near-surface temperature weakens convergence of near-surface wind, indicating the weakening of daytime urban breeze. Also, the decrease in near-surface temperature, thus decreased land-sea air temperature difference, leads to the weakening of sea breeze. Interestingly, there are occasions on which the cool-roof case produces higher near-surface temperature at late afternoon times in a region of Seoul than the conventional-roof case. This can occur when the cooling caused by the sea breeze in the conventional-roof case is dominant over the cooling due to cool roofs in the coolroof case.

Automated summary

This study shows that cool roofs in Seoul can effectively reduce surface temperature and wind speed, weakening urban breeze during the day, but this effect tends to decrease with increasing heat wave intensity.