Evaluation of updated nitric acid chemistry on ozone precursors and radiative effects

Abstract

This study shows that revising the reaction rate of NO 2 + HO· → HNO 3 improves simulated nitrogen partitioning and changes the simulated radiative effects of several short-lived climate forcers (SLCF). Both laboratory and field study analyses have found that the reaction rate should be reduced by 13-30% from current recommendations. We evaluate the GEOS-Chem model over North America with and without the recommended update using observations from the Intercontinental Chemical Transport Experiment - North America (INTEX-NA) Phase A campaign. Revising the NO 2 + HO· → HNO 3 rate coefficient improves model performance of oxidized nitrogen partitioning by increasing NO x concentrations in the upper troposphere and decreasing HNO 3 throughout the troposphere. The increase in NO x concentrations has a corresponding global increase in O 3 concentrations and local increases in sulfate aerosols, causing a perturbation in simulated radiative effects. These findings demonstrate the positive influence the mechanism update has on the partitioning of oxidized nitrogen species, the benefits it provides when compared to aircraft observations, and the simulated radiative effects that the reduction induces.