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Testing Atmospheric Oxidation in an Alabama Forest

Feiner, Philip A. and Brune, William H. and Miller, David O. and Zhang, Li and Cohen, Ronald C. and Romer, Paul S. and Goldstein, Allen H. and Keutsch, Frank N. and Skog, Kate M. and Wennberg, Paul O. and Nguyen, Tran B. and Teng, Alex P. and DeGouw, Joost and Koss, Abigail and Wild, Robert J. and Brown, Steven S. and Guenther, Alex and Edgerton, Eric and Baumann, Karsten and Fry, Juliane L. (2016) Testing Atmospheric Oxidation in an Alabama Forest. Journal of the Atmospheric Sciences, 73 (12). pp. 4699-4710. ISSN 0022-4928.

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The chemical species emitted by forests create complex atmospheric oxidation chemistry and influence global atmospheric oxidation capacity and climate. The Southern Oxidant and Aerosol Study (SOAS) provided an opportunity to test the oxidation chemistry in a forest where isoprene is the dominant biogenic volatile organic compound. Hydroxyl (OH) and hydroperoxyl (HO_2) radicals were two of the hundreds of atmospheric chemical species measured, as was OH reactivity (the inverse of the OH lifetime). OH was measured by laser-induced fluorescence (LIF) and by taking the difference in signals without and with an OH scavenger that was added just outside the instrument’s pinhole inlet. To test whether the chemistry at SOAS can be simulated by current model mechanisms, OH and HO_2 were evaluated with a box model using two chemical mechanisms: Master Chemical Mechanism, version 3.2 (MCMv3.2), augmented with explicit isoprene chemistry and MCMv3.3.1. Measured and modeled OH peak at about 10^6 cm^(−3) and agree well within combined uncertainties. Measured and modeled HO_2 peak at about 27 pptv and also agree well within combined uncertainties. Median OH reactivity cycled between about 11 s^(−1) at dawn and about 26 s^(−1) during midafternoon. A good test of the oxidation chemistry is the balance between OH production and loss rates using measurements; this balance was observed to within uncertainties. These SOAS results provide strong evidence that the current isoprene mechanisms are consistent with measured OH and HO_2 and, thus, capture significant aspects of the atmospheric oxidation chemistry in this isoprene-rich forest.

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Wennberg, Paul O.0000-0002-6126-3854
Additional Information:© 2017 American Meteorological Society. Open Choice. (Manuscript received 9 February 2016, in final form 16 August 2016) We thank the SOAS campaign organizers and leadership (A. M. Carlton, A. Goldstein, J. Jimenez, R. W. Pinder, J. de Gouw, B. J. Turpin, and A. B. Guenther), NCAR EOL personnel, and our hosts in Brent, Alabama, especially Mayor Dennis Stripling, for a successful field campaign. We also thank B. Baier for performing some model simulations and S. Kim and H. Harder for helpful conversations. SOAS financing and support was given by NSF, the NCAR Earth Observing Laboratory, and the Electric Power Research Institute. The Penn State effort was supported by NSF Grant AGS-1246918. Caltech acknowledges funding from the National Science Foundation (NSF) under Grant AGS-1240604 and NSF Postdoctoral Research Fellowship Program Award AGS-1331360. The University of Wisconsin–Madison and Harvard acknowledge funding from the National Science Foundation (NSF) under Grants AGS-1247421 and AGS-1628530.
Funding AgencyGrant Number
National Center for Atmospheric Research (NCAR)UNSPECIFIED
Electric Power Research Institute (EPRI)UNSPECIFIED
NSF Postdoctoral Research FellowshipAGS-1331360
Subject Keywords:Biosphere-atmosphere interaction; Chemistry, atmospheric
Issue or Number:12
Record Number:CaltechAUTHORS:20170213-165652994
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Official Citation:Feiner, P., W. Brune, D. Miller, L. Zhang, R. Cohen, P. Romer, A. Goldstein, F. Keutsch, K. Skog, P. Wennberg, T. Nguyen, A. Teng, J. DeGouw, A. Koss, R. Wild, S. Brown, A. Guenther, E. Edgerton, K. Baumann, and J. Fry, 2016: Testing Atmospheric Oxidation in an Alabama Forest. J. Atmos. Sci., 73, 4699–4710, doi: 10.1175/JAS-D-16-0044.1.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74284
Deposited By: George Porter
Deposited On:14 Feb 2017 15:44
Last Modified:03 Oct 2019 16:36

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