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An Observationally Constrained Evaluation of the Oxidative Capacity in the Tropical Western Pacific TroposphereHydroxyl radical (OH) is the main daytime oxidant in the troposphere and determines the atmospheric lifetimes of many compounds. We use aircraft measurements of O3, H2O, NO, and other species from the Convective Transport of Active Species in the Tropics (CONTRAST) field campaign, which occurred in the tropical western Pacific (TWP) during January-February 2014, to constrain a photochemical box model and estimate concentrations of OH throughout the troposphere. We find that tropospheric column OH (OHCOL) inferred from CONTRAST observations is 12 to 40% higher than found in chemical transport models (CTMs), including CAM-chem-SD run with 2014 meteorology as well as eight models that participated in POLMIP (2008 meteorology). Part of this discrepancy is due to a clear-sky sampling bias that affects CONTRAST observations; accounting for this bias and also for a small difference in chemical mechanism results in our empirically based value of OHCOL being 0 to 20% larger than found within global models. While these global models simulate observed O3 reasonably well, they underestimate NOx (NO +NO2) by a factor of 2, resulting in OHCOL approx.30% lower than box model simulations constrained by observed NO. Underestimations by CTMs of observed CH3CHO throughout the troposphere and of HCHO in the upper troposphere further contribute to differences between our constrained estimates of OH and those calculated by CTMs. Finally, our calculations do not support the prior suggestion of the existence of a tropospheric OH minimum in the TWP, because during January-February 2014 observed levels of O3 and NO were considerably larger than previously reported values in the TWP.
Document ID
20160013296
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Nicely, Julie M.
(Universities Space Research Association Greenbelt, MD, United States)
Anderson, Daniel C.
(Maryland Univ. College Park, MD, United States)
Canty, Timothy P.
(Maryland Univ. College Park, MD, United States)
Salawitch, Ross J.
(Maryland Univ. College Park, MD, United States)
Wolfe, Glenn M.
(Maryland Univ. College Park, MD, United States)
Apel, Eric C.
(National Center for Atmospheric Research Boulder, CO, United States)
Arnold, Steve R.
(Leeds Univ. United Kingdom)
Atlas, Elliot L.
(Miami Univ. Miami, FL, United States)
Blake, Nicola J.
(California Univ. Irvine, CA, United States)
Bresch, James F.
(National Center for Atmospheric Research Boulder, CO, United States)
Campos, Teresa L.
(University Corp. for Atmospheric Research Boulder, CO, United States)
Dickerson, Russell R.
(Maryland Univ. College Park, MD, United States)
Duncan, Bryan
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Emmons, Louisa K.
(National Center for Atmospheric Research Boulder, CO, United States)
Evans, Mathew J.
(York Univ. United Kingdom)
Fernandez, Rafael P.
(Consejo Superior de Investigaciones Cientificas Barcelona, Spain)
Flemming, Johannes
(European Centre for Medium-Range Weather Forecasts Reading, United Kingdom)
Hall, Samuel R.
(National Center for Atmospheric Research Boulder, CO, United States)
Hanisco, Thomas F.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Honomichl, Shawn B.
(National Center for Atmospheric Research Boulder, CO, United States)
Hornbrook, Rebecca S.
(National Center for Atmospheric Research Boulder, CO, United States)
Huijnen, Vincent
(Royal Netherlands Meteorological Inst. De Bilt, Netherlands)
Kaser, Lisa
(National Center for Atmospheric Research Boulder, CO, United States)
Kinnison, Douglas E.
(National Center for Atmospheric Research Boulder, CO, United States)
Lamarque, Jean-Francois
(National Center for Atmospheric Research Boulder, CO, United States)
Mao, Jingqui
(Princeton Univ. Princeton, NJ, United States)
Monks, Sarah A.
(Leeds Univ. United Kingdom)
Montzka, Denise D.
(National Center for Atmospheric Research Boulder, CO, United States)
Pan, Laura L.
(National Center for Atmospheric Research Boulder, CO, United States)
Riemer, Daniel D.
(Miami Univ. Miami, FL, United States)
Saiz-Lopez, Alfonso
(Consejo Superior de Investigaciones Cientificas Barcelona, Spain)
Steenrod, Stephen D.
(Universities Space Research Association Greenbelt, MD, United States)
Stell, Meghan H.
(University Corp. for Atmospheric Research Boulder, CO, United States)
Tilmes, Simone
(National Center for Atmospheric Research Boulder, CO, United States)
Turquety, Solene
(Paris Univ. France)
Ullmann, Kirk
(National Center for Atmospheric Research Boulder, CO, United States)
Weinheimer, Andrew J.
(National Center for Atmospheric Research Boulder, CO, United States)
Date Acquired
November 8, 2016
Publication Date
June 24, 2016
Publication Information
Publication: Journal of Geophysical Research: Atmospheres
Publisher: AGU Publications
Volume: 121
Issue: 12
ISSN: 2169-897X
Subject Category
Meteorology And Climatology
Report/Patent Number
GSFC-E-DAA-TN36706
Funding Number(s)
CONTRACT_GRANT: NA13OAR4310071
CONTRACT_GRANT: NNG11HP16A
CONTRACT_GRANT: NNH12ZDA001N-UACO
CONTRACT_GRANT: NNX15AT34A
CONTRACT_GRANT: NNH15CO48B
Distribution Limits
Public
Copyright
Other
Keywords
Hydroxyl radical
Atmospheric chemistry

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