Anthropogenic heating of the urban environment due to air conditioning

• Published in: Journal of geophysical research. Atmospheres 2014-05, Vol.119 (10), p.5949-5965
• Main Authors: Salamanca, F., Georgescu, M., Mahalov, A., Moustaoui, M., Wang, M.
• Format: Article
• Language: English
• Subjects: Air conditioning; Air temperature; Anthropogenic factors; Boundary layers; built environment; Climatology; Cooling systems; Demand; Energy consumption; Extreme heat; Geophysics; Heat transfer; Metropolitan areas; regional climate modeling; Representations; Semiarid environments; Thermal stratification; Urban areas; urban climate; Urban environments; urban heat island; Urban heat islands; Waste heat; Weather; Weather stations; Wind speed
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2013JD021225

This article investigates the effect of air conditioning (AC) systems on air temperature and examines their electricity consumption for a semiarid urban environment. We simulate a 10 day extreme heat period over the Phoenix metropolitan area (U.S.) with the Weather Research and Forecasting model coupled to a multilayer building energy scheme. The performance of the modeling system is evaluated against 10 Arizona Meteorological Network weather stations and one weather station maintained by the National Weather Service for air temperature, wind speed, and wind direction. We show that explicit representation of waste heat from air conditioning systems improved the 2 m air temperature correspondence to observations. Waste heat release from AC systems was maximum during the day, but the mean effect was negligible near the surface. However, during the night, heat emitted from AC systems increased the mean 2 m air temperature by more than 1°C for some urban locations. The AC systems modified the thermal stratification of the urban boundary layer, promoting vertical mixing during nighttime hours. The anthropogenic processes examined here (i.e., explicit representation of urban energy consumption processes due to AC systems) require incorporation in future meteorological and climate investigations to improve weather and climate predictability. Our results demonstrate that releasing waste heat into the ambient environment exacerbates the nocturnal urban heat island and increases cooling demands. Key Points AC systems increased the mean air temperature over 1°C in some urban locations Waste heat from AC improved the air temperature correspondence to observations Releasing waste heat into the ambient environment increases cooling demands