Impact of urban-industrial air pollution on chemically reactive greenhouse gases is highly sensitive to organic nitrate formation

Abstract. We compute net tropospheric ozone production (P-O₃) and methane oxidation (L-CH₄) caused by 45 days of South Korean emissions using a chemistry-transport model (CTM) and a hybrid modelling system (HMS). The CTM has global 1° x 1° resolution; the HMS has detailed chemical mechanisms and a refined regional grid (0.1° x 0.1°), but simplified, staged transport. The emissions cause +22.1 Gmol P-O₃ and +2.0 Gmol L-CH₄ in the CTM vs. +31.2 Gmol P-O₃ and +4.3 Gmol L-CH₄ in the HMS. Differences are attributed to lower volatile organic compound (VOC) reactivity in the CTM, thus decreased organic nitrate export to the free troposphere. Time-integrated O₃ mass perturbations (𝛿O₃) are similar in both models and constitute a globally-averaged +0.03 DU summertime O₃ enhancement. Due to contrasting L-CH₄, the net steady-state effective radiative forcing sustained by the emissions is +0.49 mW m^-2 in the CTM and -0.25 mW m^-2 in the HMS.