Dynamic Model Evaluation of NO_x Emissions Reductions on Ozone Concentrations in the Presence of Uncertain Emission Inventories

Abstract

The Community Multiscale Air Quality (CMAQ) model was evaluated for its ability to reproduce observed changes in ambient concentrations of ozone (O₃) for two seasons: the summer of 2002 and the summer of 2005 covering the eastern United States. These two summer periods were distinguished by large emissions reductions stemming from controls mandated by the NO_x State Implementation Plan (SIP) after 2002. CMAQ was evaluated for the robustness of its response in ambient O₃ levels to changes in NO_x emissions. Furthermore, uncertainties in the NO_x emissions inventory were propagated through the model using a direct sensitivity approach. Considering a 50% uncertainty in the area and mobile source NO_x emissions, the model was able to replicate changes in O₃ concentrations between 2002 and 2005 at most observation sites.