![]() Attaching photochemical reactivities to measurements of chemical species allows for a richer, yet more constrained-to-what-matters, set of metrics for model evaluation. The models sharply underestimate O₃ production below 4 km in both Pacific and Atlantic basins, and this can be traced to lower NO_x levels than observed. Comparing the ATom reactivities over the tropical oceans with climatological statistics from six global chemistry models, we find excellent agreement with the loss of O₃ and CH₄ but sharp disagreement with production of O₃. Surprisingly, the probability densities of species and reactivities averaged on a model scale (100 km) differ only slightly from the 2 km ATom data, indicating that much of the heterogeneity in tropospheric chemistry can be captured with current global chemistry models. In other words, accurate simulation of the least reactive 50 % of the troposphere is unimportant for global budgets. We find that 80 %–90 % of the total reactivity lies in the top 50 % of the parcels and 25 %–35 % in the top 10 %, supporting previous model-only studies that tropospheric chemistry is driven by a fraction of all the air. Six models calculated the O₃ and CH₄ photochemical tendencies from this modeling data stream for ATom 1. ![]() ![]() In this paper we present and analyze a data set of 10 s (2 km) merged and gap-filled observations of the key reactive species driving the chemical budgets of O₃ and CH₄ (O₃, CH₄, CO, H₂O, HCHO, H₂O₂, CH₃OOH, C₂H6, higher alkanes, alkenes, aromatics, NO_x, HNO₃, HNO₄, peroxyacetyl nitrate, other organic nitrates), consisting of 146 494 distinct air parcels from ATom deployments 1 through 4. The NASA Atmospheric Tomography (ATom) mission built a photochemical climatology of air parcels based on in situ measurements with the NASA DC-8 aircraft along objectively planned profiling transects through the middle of the Pacific and Atlantic oceans. Use this Persistent URL to link to this item: Heterogeneity and chemical reactivity of the remote troposphere defined by aircraft measurements. and Thompson, Chelsea and Hanisco, Thomas F. and Commane, Roisin and McKain, Kathryn and Peischl, Jeff and Ryerson, Thomas B. and Kim, Michelle and Crounse, John and Diskin, Glenn and DiGangi, Joshua and Daube, Bruce C. ![]() and Emmons, Louisa and Lacey, Forrest and Lamarque, Jean-Francois and Fiore, Arlene M. ![]()
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