Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 6 2009 10.5194/acpd-9-23623-2009 http://www.atmos-chem-phys-discuss.net/9/23623/2009/ http://www.atmos-chem-phys-discuss.net/9/23623/2009/acpd-9-23623-2009.html http://www.atmos-chem-phys-discuss.net/9/23623/2009/acpd-9-23623-2009.pdf 23623 23664 2009-11-05 Finding the missing stratospheric Br_y: a global modeling study of CHBr₃ and CH₂Br₂ Q. Liang R. S. Stolarski S. R. Kawa J. E. Nielsen J. M. Rodriguez A. R. Douglass D. R. Blake E. L. Atlas L. Ott NASA Goddard Space Flight Center, Atmospheric Chemistry and Dynamics Branch, Code 613.3, Greenbelt, MD 20771, USA Oak Ridge Associated Universities, NASA Postdoctoral Program, Oak Ridge, Tennessee 37831, USA NASA Goddard Space Flight Center, Global Modeling and Assimilation Office, Code 610.1, Greenbelt, MD 20771, USA Science Systems and Applications Inc., Lanham, Maryland, USA University of California, 570 Rowland Hall, Irvine, CA 92697, USA University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA Goddard Earth Sciences and Technology Center, University of Maryland, Baltimore County, Maryland, USA Recent in situ and satellite measurements suggest a contribution of ~5 pptv to stratospheric inorganic bromine from short-lived bromocarbons. We conduct a modeling study of the two most important short-lived bromocarbons, bromoform (CHBr₃) and dibromomethane (CH₂Br₂), with the Goddard Earth Observing System Chemistry Climate Model (GEOS CCM) to account for this missing stratospheric bromine. We derive a "top-down" emission estimate of CHBr₃ and CH₂Br₂ using airborne measurements in the Pacific and North American troposphere and lower stratosphere (LS) obtained during previous NASA aircraft campaigns. Our emission estimate suggests that to reproduce the observed concentrations in the free troposphere, a global oceanic emission of 425 Gg Br yr^−1 for CHBr₃ and 57 Gg Br yr^−1 for CH₂Br₂ is needed, with 60% of emissions from open ocean and 40% from coastal regions. Although our simple emission scheme assumes no seasonal variations, the model reproduces the observed seasonal variations of the short-lived bromocarbons with high concentrations in winter and low concentrations in summer. 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