From NASA’s Atmospheric Tomography (ATom) mission, we calculate the average production/loss of O₃ and CH₄ for 10s air parcels along profiling transects through the Pacific/Atlantic Oceans for four seasons. We find photochemically hot air masses on all scales from 2 to 2000 km. Tropical production of O₃ is high (~2 ppb/day) throughout the ATom profiles (0–12 km). In the Eastern Pacific we find large coherent air masses of extremely high reactivities in August (monsoonal) and May (biomass burning). The tropics dominate the O₃ and CH₄ budgets. Sensitivity analysis identifies only five critical species (NOx, O₃, CH₄, CO, and H₂O) responsible for driving the budgets. Sensitivity analysis shows large 2^nd-order effects for coupled perturbations, indicating that 1^st-order sensitivities cannot simply be added. Feedback analysis indicates a slower-than-expected timescale for decay of O₃ perturbations. ATom data shows how global tropospheric chemistry is constructed from a myriad of fine and large scales.