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Volume 17, issue 16 | Copyright
Atmos. Chem. Phys., 17, 9917-9930, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 23 Aug 2017

Research article | 23 Aug 2017

Modeling the inorganic bromine partitioning in the tropical tropopause layer over the eastern and western Pacific Ocean

Maria A. Navarro1, Alfonso Saiz-Lopez2, Carlos A. Cuevas2, Rafael P. Fernandez3, Elliot Atlas1, Xavier Rodriguez-Lloveras2, Douglas Kinnison4, Jean-Francois Lamarque4, Simone Tilmes4, Troy Thornberry5,6, Andrew Rollins5,6, James W. Elkins5, Eric J. Hintsa5,6, and Fred L. Moore5,6 Maria A. Navarro et al.
  • 1Department of Atmospheric Sciences, RSMAS, University of Miami, Miami, Florida, USA
  • 2Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid, Spain
  • 3National Research Council (CONICET), FCEN-UNCuyo, UTN-FRM, Mendoza, Argentina
  • 4Atmospheric Chemistry Observations & Modeling Laboratory, National Center for Atmospheric Research, Boulder, Colorado, USA
  • 5National Oceanic & Atmospheric Administration, Earth System Research Laboratory, Boulder, Colorado, USA
  • 6Cooperative Institute for Research in Environmental Science, University of Colorado, Boulder, Colorado, USA

Abstract. The stratospheric inorganic bromine (Bry) burden arising from the degradation of brominated very short-lived organic substances (VSLorg) and its partitioning between reactive and reservoir species is needed for a comprehensive assessment of the ozone depletion potential of brominated trace gases. Here we present modeled inorganic bromine abundances over the Pacific tropical tropopause based on aircraft observations of VSLorg from two campaigns of the Airborne Tropical TRopopause EXperiment (ATTREX 2013, carried out over the eastern Pacific, and ATTREX 2014, carried out over the western Pacific) and chemistry-climate simulations (along ATTREX flight tracks) using the specific meteorology prevailing. Using the Community Atmosphere Model with Chemistry (CAM-Chem) we model that BrO and Br are the daytime dominant species. Integrated across all ATTREX flights, BrO represents ∼43 and 48% of daytime Bry abundance at 17km over the western and eastern Pacific, respectively. The results also show zones where Br/BrO>1 depending on the solar zenith angle (SZA), ozone concentration, and temperature. On the other hand, BrCl and BrONO2 were found to be the dominant nighttime species with ∼ 61 and 56% of abundance at 17km over the western and eastern Pacific, respectively. The western-to-eastern differences in the partitioning of inorganic bromine are explained by different abundances of ozone (O3), nitrogen dioxide (NO2), total inorganic chlorine (Cly), and the efficiency of heterogeneous reactions of bromine reservoirs (mostly BrONO2 and HBr) occurring on ice crystals.

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Inorganic bromine (Bry) plays an important role in ozone layer depletion. Based on aircraft observations of organic bromine species and chemistry simulations, we model the Bry abundances over the Pacific tropical tropopause. Our results show BrO and Br as the dominant species during daytime hours, and BrCl and BrONO2 as the nighttime dominant species over the western and eastern Pacific, respectively. The difference in the partitioning is due to changes in the abundance of O3, NO2, and Cly.
Inorganic bromine (Bry) plays an important role in ozone layer depletion. Based on aircraft...