Ozone and Related Trace Gases over the Atlantic and Pacific Oceans: Comparison of Results from the ATom Mission and Model Studies

The NASA Atmospheric Tomography (ATom) Mission is designed to study ozone chemistry and methane oxidation on large scales and to test chemical transport models. To carry this out, the NASA DC-8 aircraft was outfitted with a large payload of instruments for reactive and trace gases, aerosols, radiation and meteorology, with flights from north to south over the Pacific, returning over the Atlantic. Thus far in ATom, vertical cross sections of the atmosphere have been measured in summer and winter seasons in both hemispheres. We will present data and intercomparisons from the first two ATom deployments, including analysis of the distributions of ozone and related gas phase species. The presentation will focus on comparison and analysis of measured data from the DC-8 and model results along flight tracks (time series), probability distributions along N-S transects over the Atlantic and Pacific Oceans and the polar regions as a function of altitude, latitude, type of air mass, and season, and correlations between important and related trace species. The goal is to better understand model-measurement agreement or differences resulting from chemistry and transport. Based on preliminary analyses, the NASA Global Modeling Initiative (GMI) chemical transport model provides an accurate overall hindcast of ozone distributions in ATom-1. Some discrepancies exist between model and measured data over the tropical Atlantic. The tropical Atlantic had much higher ozone levels throughout the troposphere in ATom-1 (August 2016) than the Pacific, nearly twice as much on average, which is largely captured by the model. Further work will include extending the analyses to ATom-2 (February 2017), examining the origin of air masses with high (and low) ozone in ATom, bringing more models into the comparison, and exploring the chemical relationships in models and measured data for ozone and related species.