Exploring oxidation in the remote free troposphere: Insights from Atmospheric Tomography (ATom)

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 within 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.

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Author Brune, W.H.
Miller, D.O.
Thames, A.B.
Allen, H.M.
Apel, Eric
Blake, D.R.
Bui, T.P.
Commane, R.
Crounse, J.D.
Daube, B.C.
Diskin, G.S.
DiGangi, J.P.
Elkins, J.W.
Hall, Samuel
Hanisco, T.F.
Hannun, R.A.
Hintsa, E.J.
Hornbrook, Rebecca
Kim, M.J.
McKain, K.
Moore, F.L.
Neuman, J.A.
Nicely, J.M.
Peischl, J.
Ryerson, T.B.
St. Clair, J.M.
Sweeney, C.
Teng, A.P.
Thompson, C.
Ullmann, Kirk
Veres, P.R.
Wennberg, P.O.
Wolfe, G.M.
Publisher UCAR/NCAR - Library
Publication Date 2020-01-16T00:00:00
Digital Object Identifier (DOI) Not Assigned
Alternate Identifier N/A
Resource Version N/A
Topic Category geoscientificInformation
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Metadata Date 2023-08-18T19:08:42.712209
Metadata Record Identifier edu.ucar.opensky::articles:23064
Metadata Language eng; USA
Suggested Citation Brune, W.H., Miller, D.O., Thames, A.B., Allen, H.M., Apel, Eric, Blake, D.R., Bui, T.P., Commane, R., Crounse, J.D., Daube, B.C., Diskin, G.S., DiGangi, J.P., Elkins, J.W., Hall, Samuel, Hanisco, T.F., Hannun, R.A., Hintsa, E.J., Hornbrook, Rebecca, Kim, M.J., McKain, K., Moore, F.L., Neuman, J.A., Nicely, J.M., Peischl, J., Ryerson, T.B., St. Clair, J.M., Sweeney, C., Teng, A.P., Thompson, C., Ullmann, Kirk, Veres, P.R., Wennberg, P.O., Wolfe, G.M.. (2020). Exploring oxidation in the remote free troposphere: Insights from Atmospheric Tomography (ATom). UCAR/NCAR - Library. http://n2t.net/ark:/85065/d71v5j3x. Accessed 23 June 2025.

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