Global and regional effects of the photochemistry of CH3O2NO2: evidence from ARCTAS

Using measurements from the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) experiment, we show that methyl peroxy nitrate (CH3 O2 NO2 ) is present in concentrations of ∼5–15 pptv in the springtime arctic upper troposphere. We investigate the regional and global effects of CH3 O2 NO2 by including its chemistry in the GEOS-Chem 3-D global chemical transport model. We find that at temperatures below 240 K inclusion of CH3 O2 NO2 chemistry results in decreases of up to ∼20 % in NOx , ∼20 % in N2 O5 , ∼5 % in HNO3 , ∼2 % in ozone, and increases in methyl hydrogen peroxide of up to ∼14 %. Larger changes are observed in biomass burning plumes lofted to high altitude. Additionally, by sequestering NOx at low temperatures, CH3 O2 NO2 decreases the cycling of HO2 to OH, resulting in a larger upper tropospheric HO2 to OH ratio. These results may impact some estimates of lightning NOx sources as well as help explain differences between models and measurements of upper tropospheric composition.