10.2 Observational Constraints on a Potential Source of Secondary Methanol

Thursday, 11 January 2018: 8:45 AM
Room 18CD (ACC) (Austin, Texas)
Michelle Kim, California Institute of Technology, Pasadena, CA; and J. Crounse, A. P. Teng, E. Asher, A. Hills, R. Hornbrook, E. C. Apel, A. L. Brosius, D. O. Miller, A. Thames, W. Brune, K. Ullman, S. Hall, J. St. Clair, G. M. Wolfe, T. Hanisco, C. Sweeney, K. McKain, J. Peischl, C. Thompson, T. B. Ryerson, R. Commane, B. C. Daube, S. Wofsy, and P. Wennberg

The reaction between methyl peroxy (CH3OO) and hydroxyl (OH) radicals was recently demonstrated in laboratory experiments to proceed at a atmospherically relevant rate [0.8-2.8E-10 cm3 s−1]. A minor branching from this reaction is calculated to yield methanol (CH3OH). Global atmospheric models coupled with theoretical calculations suggest that this reaction may result in a secondary source of CH3OH that rivals emissions from the terrestrial biosphere. In the remote atmosphere, methane (CH4) oxidation by hydroxyl radicals (OH) produce methyl peroxy radicals (CH3OO). In addition to its reaction with OH, CH3OO will undergo reaction with RO2, a previously known source of methanol, or with either NO (to generate formaldehyde (CH2O)) or HO2 (to generate methyl hydrogen peroxide (CH3OOH)), a relatively longer-lived radical reservoir. In-situ measurements of photolysis rates, CH4, OH, HO2, NO, CH3OOH, CH2O, CH3OH, OH, and HO2 from the ATom campaign offer observational constraints on the relative importance of these pathways with potential significance for persistent gaps in our understanding of global methanol and the oxidant budget in the remote atmosphere.
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