Impact of Cool Roofs on Urban Energy Utilization in a Future Warm Climate

Urban Heat Islands (UHIs) have been studied extensively.  However, they have recently received greater attention due to their impact on the environmental, health and energy sectors.  In a recent paper by Tewari et al (2016), UHIs and their interaction with heat waves under current and future climate conditions were investigated.  Salamanca et al (2014, 2015) examined the effect of air conditioning (AC) systems on air temperature and their energy consumption in a semi-arid environment.  They found that explicit representation of waste heat from AC systems improved the modelling of 2m air temperature in comparison to local observations.  They also found that during the night, heat emitted from AC systems increased the mean 2m air temperature by more than 1°C for some urban locations.

We will present the preliminary results of our study of the impacts of AC systems under future urban climate projections and the impact of cooler building roofs as a mitigation strategy given the assumption of increased use of AC systems.  The energy usage under the current climate is evaluated by conducting numerical experiments using a regional atmospheric model WRF (Weather Research and Forecasting model) coupled with a multi-layer urban canopy model for a summer month (June 2012).  For these experiments, NCEP FNL (Final Global Analysis) data are used to forced the regional model.  To represent the future climate state, the current climate data (i.e., from FNL) were perturbed using forcing data from a global climate model (CCSM4).