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Exploring Oxidation in the Remote Free Troposphere: Insights from Atmospheric Tomography (ATom)

Brune, W. H. and Allen, H. M. and Crounse, J. D. and Kim, M. J. and Teng, A. P. and Wennberg, P. O. (2020) Exploring Oxidation in the Remote Free Troposphere: Insights from Atmospheric Tomography (ATom). Journal of Geophysical Research. Atmospheres, 125 (1). Art. No. e2019JD031685. ISSN 2169-897X. https://resolver.caltech.edu/CaltechAUTHORS:20200102-145133388

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Abstract

Earth's atmosphere oxidizes the greenhouse gas methane and other gases, thus determining their lifetimes and oxidation products. Much of this oxidation occurs in the remote, relatively clean free troposphere above the planetary boundary layer, where the oxidation chemistry is thought to be much simpler and better understood than it is in urban regions or forests. The NASA airborne Atmospheric Tomography study (ATom) was designed to produce cross sections of the detailed atmospheric composition in the remote atmosphere over the Pacific and Atlantic Oceans during four seasons. As part of the extensive ATom data set, measurements of the atmosphere's primary oxidant, hydroxyl (OH), and hydroperoxyl (HO₂) are compared to a photochemical box model to test the oxidation chemistry. Generally, observed and modeled median OH and HO₂ agree to with combined uncertainties at the 2σ confidence level, which is ~±40%. For some seasons, this agreement is within ~±20% below 6 km altitude. While this test finds no significant differences, OH observations increasingly exceeded modeled values at altitudes above 8 km, becoming ~35% greater, which is near the combined uncertainties. Measurement uncertainty and possible unknown measurement errors complicate tests for unknown chemistry or incorrect reaction rate coefficients that would substantially affect the OH and HO₂ abundances. Future analysis of detailed comparisons may yield additional discrepancies that are masked in the median values.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2019jd031685DOIArticle
https://doi.org/10.3334/ORNLDAAC/1581DOIData
ORCID:
AuthorORCID
Crounse, J. D.0000-0001-5443-729X
Wennberg, P. O.0000-0002-6126-3854
Additional Information:© 2019 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Received 17 SEP 2019; Accepted 19 DEC 2019; Accepted article online 27 DEC 2019. The authors thank the NASA ATom management team, pilots, logistical support team, aircraft operations team, and fellow scientists. Data and Model Availability: The data and model used in this paper are publicly available: data: https://doi.org/10.3334/ORNLDAAC/1581; model framework: https://sites.google.com/site/wolfegm/models; MCMv331 chemical mechanism: http://mcm.leeds.ac.uk/MCM/. Author Contribution: DOM, WHB, and ABT made the OH and HO2 measurements, performed the model runs, analyzed the data, and wrote the initial draft of the manuscript. GMW provided support the F0AM model framework. WHB, DOM, ABT, HMA, ECA. DRB, TPB, RC, JDC, BCD, GSD, JPD, JWE, SRH, TFH, RAH, EJH, RSH, MJK, KM, FLM, JMN, JAN, JP, TBR, JMS CS., APT, CT, KU, PRV, POW, GMW provided ATom measurements used for the modeling and edits for the manuscript. The authors declare no financial or affiliation conflicts-of-interest. This study was supported by the NASA grant NNX15AG59A. This material is based upon work supported by the National Center for Atmospheric Research, which is a major facility sponsored by the National Science Foundation under Cooperative Agreement No. 1852977. MJK was supported by NSF fellowship 1524860 for the first year of this study.
Funders:
Funding AgencyGrant Number
NASANNX15AG59A
National Center for Atmospheric Research (NCAR)UNSPECIFIED
NSFAGS-1852977
NSF Postdoctoral FellowshipAGS-1524860
Subject Keywords:hydroxyl; atmospheric chemistry; remote troposphere
Issue or Number:1
Record Number:CaltechAUTHORS:20200102-145133388
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200102-145133388
Official Citation:Brune, W. H., Miller, D. O., Thames, A. B., Allen, H. M., Apel, E. C., Blake, D. R., et al. (2020). Exploring oxidation in the remote free troposphere: Insights from Atmospheric Tomography (ATom). Journal of Geophysical Research: Atmospheres, 125, e2019JD031685. https://doi.org/10.1029/2019JD031685
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100469
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:03 Jan 2020 02:47
Last Modified:14 Jan 2020 22:31

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