04 Oct 2022
04 Oct 2022
Status: a revised version of this preprint is currently under review for the journal ACP.

Heterogeneity and chemical reactivity of the remote troposphere defined by aircraft measurements

Hao Guo1, Clare M. Flynn2, Michael J. Prather1, Sarah A. Strode3, Stephen D. Steenrod3, Louisa Emmons4, Forrest Lacey4,5, Jean-Francois Lamarque4, Arlene M. Fiore6, Gus Correa6, Lee T. Murray7, Glenn M. Wolfe3,8, Jason M. St. Clair3,8, Michelle Kim9, John Crounse10, Glenn Diskin10, Joshua DiGangi10, Bruce C. Daube11,12, Roisin Commane11,12, Kathryn McKain13,14, Jeff Peischl14,15, Thomas B. Ryerson13,15, Chelsea Thompson13, Thomas F. Hanisco3, Donald Blake16, Nicola J. Blake16, Eric C. Apel4, Rebecca S. Hornbrook4, James W. Elkins14, Eric J. Hintsa13,14, Fred L. Moore13,14, and Steven C. Wofsy11 Hao Guo et al.
  • 1Department of Earth System Science, University of California, Irvine, CA 92697
  • 2Department of Meteorology, Stockholm University, Stockholm SE-106 91, Sweden
  • 3Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771
  • 4Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO 80301
  • 5Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309
  • 6Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964
  • 7Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14611
  • 8Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Baltimore, MD 21228
  • 9Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
  • 10Atmospheric Composition, NASA Langley Research Center, Hampton VA 23666
  • 11John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
  • 12Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138
  • 13Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309
  • 14Global Monitoring Division, Earth System Research Laboratory, NOAA, Boulder, CO 80305
  • 15Chemical Sciences Division, National Oceanic and Atmospheric Administration Earth System Research Laboratory, Boulder, CO 80305
  • 16Department of Chemistry, University of California, Irvine, CA 92697

Abstract. 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. 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, NOx, HNO3, HNO4, peroxyacetyl nitrate, other organic nitrates), consisting of 146,494 distinct air parcels from ATom deployments 1 through 4. Six models calculated the O3 and CH4 photochemical tendencies from this modeling data stream for ATom 1. 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. In other words, accurate simulation of the least reactive 50 % of the troposphere is unimportant for global budgets. 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. Comparing the ATom reactivities over the tropical oceans with climatological statistics from six global chemistry models, we find generally good agreement with the reactivity rates for O3 and CH4. In the Pacific but not Atlantic, however, models distinctly underestimate O3 production below 2 km, and this can be traced lower NOX levels than observed. Attaching photochemical reactivities to measurements of chemical species allows for a richer, yet more constrained-to-what-matters, set of metrics for model evaluation.

Hao Guo et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-631', Anonymous Referee #1, 02 Nov 2022
    • AC1: 'Reply on RC1 & RC2', Michael Prather, 09 Nov 2022
  • RC2: 'Comment on acp-2022-631', Anonymous Referee #2, 02 Nov 2022
    • AC2: 'Reply on RC2', Michael Prather, 09 Nov 2022

Hao Guo et al.


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Short summary
We have prepared from the recent ATom aircraft mission a unique and unusual result: a measurement-based derivation of the production and loss rates of ozone and methane over the ocean basins. These are the key products of chemistry models used in assessments but have thus far lacked observational metrics. It also shows the scales of variability of atmospheric chemical rates and provides a major challenge to the atmospheric models.