. Measured and modeled ozone distributions over the Atlantic and Pacific Oceans from the ATom mission

Abstract
Field deployments of the NASA Atmospheric Tomography (ATom) Mission in 2016-2018 have provided a large set of chemical and other data over the Atlantic, Pacific, Southern, and Arctic Oceans from near the surface to about 12 km in each season. The mission was designed to study ozone and methane chemistry, atmospheric oxidation, and other chemical cycles on large scales, and to challenge chemical transport models. I will present data and intercomparisons from ATom deployments, focusing on analysis of the distributions of ozone, related gas phase species, and model results (some from arbitrary years and some using meteorology from the ATom time periods, with results mapped onto ATom flight tracks). The goals are to 1) find the distributions of tropospheric ozone along N-S transects across the Atlantic and Pacific Oceans and the polar regions as a function of altitude, latitude, and season, 2) compare with model results both along flight tracks and as probability distributions, and 3) improve our understanding of model-measurement agreement or differences resulting from chemistry and transport. All the models examined do a reasonable job of predicting large-scale features in ozone. The NASA Global Modeling Initiative (GMI) chemical transport model performed well in hindcasting ozone distributions in ATom-1 and 2 using actual meteorology. Some discrepancies exist between model and measured data over the tropical Atlantic, where ozone observed during ATom was much higher compared to the tropical Pacific throughout the troposphere. Further work includes exploring the origin of air masses with high (and low) ozone in ATom, extending the analyses to the last two ATom deployments, and exploring the chemical relationships in models and measured data for ozone and other species.