High ozone concentrations on hot days: The role of electric power demand and NOx emissions

Abstract

High ambient temperatures intensify photochemical production of tropospheric ozone, leading to concerns that global warming may exacerbate smog episodes. This widely observed phenomenon has been termed the climate penalty factor (CPF). A variety of meteorological and photochemical processes have been suggested to explain why surface ozone increases on hot days. Here, we quantify an anthropogenic factor previously overlooked: the rise of ozone precursor emissions on hot summer days due to high electricity demand. Between 1997 and 2011, power plant emissions of NOx in the eastern U.S. increased by ∼2.5-4.0%/°C, raising surface NOx concentrations by 0.10-0.25 ppb/°C. Given an ozone production efficiency (OPE) of ∼8 mol/mol based on the 2011 NASA DISCOVER-AQ campaign, at least one third of the CPF observed in the eastern U.S. can be attributed to the temperature dependence of NO x emissions. This finding suggests that controlling emissions associated with electricity generation on hot summer days can mitigate the CPF. Key Points Quantify the CPF to power plant emissions Estimate the ozone production efficiency in the eastern US Power plants emissions on hot summer days need further regulation ©2013. American Geophysical Union. All Rights Reserved.