edu.ucar.opensky::articles:18612 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T02:48:10.621061 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7gb25pq An observationally constrained evaluation of the oxidative capacity in the tropical western Pacific troposphere 2016-06-27T00:00:00Z publication https://n2t.org/ark:/85065/d7gb25pq https://doi.org/10.1002/2016JD025067 Nicely, J. author Anderson, D. author Canty, T. author Salawitch, R. author Wolfe, G. author Apel, Eric C. author Arnold, S. author Atlas, E. author Blake, N. author Bresch, James author Campos, Teresa author Dickerson, R. author Duncan, B. author Emmons, Louisa K. author Evans, M. author Fernandez, R. author Fleming, J. author Hall, Samuel R. author Hanisco, T. author Honomichl, Shawn B. author Hornbrook, Rebecca author Huijnen, V. author Kaser, Lisa author Kinnison, Douglas E. author Lamarque, Jean-François author Mao, J. author Monks, S. author Montzka, Denise D. author Pan, Laura L. author Riemer, D. author Saiz-Lopez, A. author Steenrod, S. author Stell, Meghan author Tilmes, Simone author Turquety, S. author Ullmann, Kirk author Weinheimer, Andrew author UCAR/NCAR - Library publisher Hydroxyl 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 ~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. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2016 American Geophysical Union. None eng geoscientificInformation