Effects of Increasing Roof Albedo on the Urban Environment

Rapid urbanization has intensified summer heat waves in recent decades in the background of global warming. In this study, a record-breaking heat wave occurred in Beijing during July 13-15, 2002 was simulated using WRF2.2 coupled with an urban canopy model. The modeled diurnal air temperature in the city compared well with a station observation. The wind convergence caused by urban heat island effect was also presented. By increasing roof albedo, effect of urban heat island was reduced due to decreased net radiation and sensible heat flux. Because of the decreased urban heating intensity, the simulated wind convergence in the downwind of the urban area was weakened, which may contribute to the dilution of air pollution. In addition, comparison of modeled air temperatures which individually considered the high-albedo cooling effect and the foehn effect illustrated that increases in roof albedo can offset the foehn warming during the heat wave in Beijing.