Measured and Modeled Ozone Distributions over the Atlantic and Pacific Oceans from ATom and Other Studies

Field deployments of the NASA Atmospheric Tomography (ATom) Mission recently concluded, providing a large data set of chemical and other measurements over the Atlantic, Pacific, Southern, and Arctic Oceans from near the surface to about 12 km in each season. The mission is 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 and earlier studies, 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 previous data from HIPPO (2009-2011), and exploring the chemical relationships in models and measured data for ozone and other species.