Investigating the potential for cool roofs to mitigate urban heat in the Kansas City metropolitan area

An urban heat island (UHI) is a phenomenon where the temperatures within cities are greater than those of surrounding rural areas due to human activity and physical properties of urban surfaces. One method that has been investigated as a way to mitigate the UHI phenomenon is to increase the surface albedo in cities, which reflects a greater amount of solar radiation away from these surfaces compared to conventional materials (e.g., dark asphalt shingles). In this study, we utilize the Weather Research and Forecasting (WRF) model to investigate the UHI under different scenarios during a July 2012 heat wave event in the Kansas City metropolitan area (KCMA). Two cool roof simulations are implemented to determine the effectiveness of this mitigation strategy on reducing temperatures within the KCMA. The first scenario represents "newly installed" cool roofs with an albedo of 0.8 and the second with "aged" cool roofs with an albedo of 0.5. Results indicate that cool roof materials were able to mitigate the UHI effect by up to 0.64 degrees C during the evening, causing the onset of the UHI effect to be delayed until later in the day. Cool roofs were also shown to have important impacts on the surface energy balance, affecting both sensible and ground storage heat fluxes, and the planetary boundary layer.