The NASA Atmospheric Tomography (ATom) missions provides unique measurements of atmospheric composition on four seasonal, meridional, profiling transects of the central Pacific and Atlantic Oceans. These observations provide most all of the key chemical constituents involved in the photochemical reactions controlling the greenhouse gases ozone and methane over the vast, remote ocean basins. Flight paths are preset to give a representative, objective profiling of air parcels throughout the troposphereas measurable with the DC8 (0.5 up to 12 km), and where most of the photochemical loss of ozone and methane occurs.

We have just completed the full reactivity data stream for all 4 deployments, providing the model-derived 24-hour average rates for the production and loss of ozone and methane in each 10-sec air parcel (143,000 in all) along the ATom flight tracks. We examine the sensitivity of the chemical reactivity to each species and to co-varying pairs. We look at the scale of heterogeneity observed at the 10-sec resolution to determine if the hottest parcels are sampled and can be represented in the models. We also test how the spatial averaging that occurs in models might affect the overall budgets for ozone and methane.