Coupled evolution of BrOx-ClOx-HOx-NOx chemistry during bromine-catalyzed ozone depletion events in the arctic boundary layer

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Read Full Article (file size: 2250184 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D4, 8368, doi:10.1029/2002JD002732, 2003 Coupled evolution of BrO_x-ClO_x-HO_x-NO_x chemistry during bromine-catalyzed ozone depletion events in the arctic boundary layer M. J. Evans Division of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, USA D. J. Jacob Division of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, USA E. Atlas Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA C. A. Cantrell Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA F. Eisele Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA F. Flocke Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA A. Fried Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA R. L. Mauldin Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA B. A. Ridley Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA B. Wert Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA Chemistry Department, University of Colorado, Boulder, Colorado, USA R. Talbot Climate Change Research Center, University of New Hampshire, Durham, New Hampshire, USA D. Blake Chemistry Department, University of California, Irvine, Irvine, California, USA B. Heikes School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA J. Snow School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA J. Walega Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA A. J. Weinheimer Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA J. Dibb Climate Change Research Center, University of New Hampshire, Durham, New Hampshire, USA Abstract Extensive chemical characterization of ozone (O₃) depletion events in the Arctic boundary layer during the TOPSE aircraft mission in March–May 2000 enables analysis of the coupled chemical evolution of bromine (BrO_x), chlorine (ClO_x), hydrogen oxide (HO_x) and nitrogen oxide (NO_x) radicals during these events. We project the TOPSE observations onto an O₃ chemical coordinate to construct a chronology of radical chemistry during O₃ depletion events, and we compare this chronology to results from a photochemical model simulation. Comparison of observed trends in ethyne (oxidized by Br) and ethane (oxidized by Cl) indicates that ClO_x chemistry is only active during the early stage of O₃ depletion (O₃ > 10 ppbv). We attribute this result to the suppression of BrCl regeneration as O₃ decreases. Formaldehyde and peroxy radical concentrations decline by factors of 4 and 2 respectively during O₃ depletion and we explain both trends on the basis of the reaction of CH₂O with Br. Observed NO_x concentrations decline abruptly in the early stages of O₃ depletion and recover as O₃ drops below 10 ppbv. We attribute the initial decline to BrNO₃ hydrolysis in aerosol, and the subsequent recovery to suppression of BrNO₃ formation as O₃ drops. Under halogen-free conditions we find that HNO₄ heterogeneous chemistry could provide a major NO_x sink not included in standard models. Halogen radical chemistry in the model can produce under realistic conditions an oscillatory system with a period of 3 days, which we believe is the fastest oscillation ever reported for a chemical system in the atmosphere. Published 28 February 2003. Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0317 Atmospheric Composition and Structure: Chemical kinetic and photochemical properties; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry. Read Full Article (file size: 2250184 bytes) Cited by Citation: Evans, M. J., et al. (2003), Coupled evolution of BrO_x-ClO_x-HO_x-NO_x chemistry during bromine-catalyzed ozone depletion events in the arctic boundary layer, J. Geophys. Res., 108(D4), 8368, doi:10.1029/2002JD002732. Copyright 2003 by the American Geophysical Union.

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