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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-572
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
07 Jul 2017
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This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
BrO and Bry profiles over the Western Pacific: Relevance of Inorganic Bromine Sources and a Bry Minimum in the Aged Tropical Tropopause Layer
Theodore K. Koenig1,2, Rainer Volkamer1,2, Sunil Baidar1,2,a, Barbara Dix1, Siyuan Wang2,3, Daniel C. Anderson4,b, Ross J. Salawitch4,5,6, Pamela A. Wales5, Carlos A. Cuevas7, Rafael P. Fernandez7,8, Alfonso Saiz-Lopez7, Mathew J. Evans9, Tomás Sherwen9, Daniel J. Jacob10,11, Johan Schmidt12, Douglas Kinnison13, Jean-François Lamarque13, Eric C. Apel13, James C. Bresch13, Teresa Campos13, Frank M. Flocke13, Samuel R. Hall13, Shawn B. Honomichl13, Rebecca Hornbrook13, Jørgen B. Jensen13, Richard Lueb13, Denise D. Montzka13, Laura L. Pan13, J. Michael Reeves13, Sue M. Schauffler13, Kirk Ullmann13, Andrew J. Weinheimer13, Elliot L. Atlas14, Valeria Donets14, Maria A. Navarro14, Daniel Riemer14, Nicola J. Blake15, Dexian Chen16, L. Gregory Huey16, David J. Tanner16, Thomas F. Hanisco17, and Glenn M. Wolfe17,18 1Department of Chemistry & Biochemistry, University of Colorado, Boulder, CO, USA
2Cooperative Institute for Research in Environmental Sciences (CIRES), Boulder, CO, USA
3Department of Chemistry, University of Michigan, Ann Arbor, MI, USA
4Department of Atmospheric & Oceanic Science, University of Maryland, College Park, MD, USA
5Department of Chemistry & Biochemistry, University of Maryland, College Park, MD, USA
6Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
7Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, Spanish National Research Council (CSIC), Madrid, Spain
8Argentine National Research Council (CONICET), FCEN-UNCuyo, UNT-FRM, Mendoza, Argentina
9Wolfson Atmospheric Chemistry Laboratories (WACL), Department of Chemistry, University of York, York, United Kingdom
10John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
11Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
12Department of Chemistry, Copenhagen University, Copenhagen, Denmark
13National Center for Atmospheric Research (NCAR), Boulder, CO, USA
14Department of Atmospheric Science, Rosenstiel School of Marine & Atmospheric Sciences (RSMAS), University of Miami, Miami, FL, USA
15Department of Chemistry, University of California, Irvine, CA, USA
16School of Earth & Atmospheric Sciences, Georgia Tech, Atlanta, Georgia, USA
17Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
18Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Maryland, USA
anow at: National Oceanic and Atmospheric Administration (NOAA), Boulder, CO, USA
bnow at: Department of Chemistry, University of Drexel, Philadelphia, PA, USA
Abstract. We report measurements of bromine monoxide (BrO) and use an observationally constrained chemical box-model to infer total gas phase inorganic bromine (Bry) over the tropical Western Pacific Ocean (tWPO) during the CONTRAST field campaign (January–February 2014). The median tropospheric BrO Vertical Column Density (VCD) over the tWPO was measured as 1.6 × 1013 molec cm−2, compared to model predictions of 0.4 × 1013 in CAM-Chem, 0.9 × 1013 in GEOS-Chem, and 2.1 × 1013 in GEOS-Chem with a sea-salt aerosol (SSA) bromine source. The observed BrO and inferred Bry profiles is found to be C-shaped in the troposphere, with local maxima in the marine boundary layer (MBL) and in the upper free troposphere. Neither global model fully captures this profile shape. Between 6 and 13.5 km, the inferred Bry is highly sensitive to assumptions about the rate of heterogeneous bromine recycling (depends on the surface area of ice/aerosols), and the inclusion of a SSA bromine source. A local Bry maximum of 3.6 ppt (2.3–11.1 ppt, 95 % CI) is observed between 9.5 and 13.5 km in air masses influenced by recent convective outflow. Unlike BrO, which increases from the convective TTL to the aged TTL, gas phase Bry decreases from the convective TTL to the aged TTL. Analysis of gas phase Bry against multiple tracers (CFC-11, H2O / O3 ratio, and θ) reveals a Bry minimum of 2.7 ppt (2.4–3.0 ppt, 95 % CI) in the aged TTL, which is remarkably insensitive to assumptions about heterogeneous chemistry. Bry increases to 6.3 ppt (5.9–6.7 ppt, 95 % CI) in the stratospheric middleworld, and 6.9 ppt (6.7–7.1 ppt, 95 % CI) in the stratospheric overworld. The local Bry minimum in the aged TTL is qualitatively (but not quantitatively) captured by CAM-chem, and suggests a more complex partitioning of gas phase and aerosol Bry species than previously recognized. Our data provide corroborating evidence that inorganic bromine sources (e.g., SSA derived gas phase Bry) are needed to explain the gas phase Bry budget in the TTL. They are also consistent with observations of significant bromide in UTLS aerosols. The total Bry budget in the TTL is currently not closed, because of the lack of concurrent quantitative measurements of gas phase Bry species (i.e., BrO, HOBr, HBr, etc.) and aerosol bromide. These simultaneous measurements are needed 1) to quantify SSA derived Bry aloft, 2) to test Bry partitioning, and explain the gas phase Bry minimum in the aged TTL, 3) to constrain heterogeneous reaction rates of bromine, and 4) to account for all of the sources of Bry to the lower stratosphere.

Citation: Koenig, T. K., Volkamer, R., Baidar, S., Dix, B., Wang, S., Anderson, D. C., Salawitch, R. J., Wales, P. A., Cuevas, C. A., Fernandez, R. P., Saiz-Lopez, A., Evans, M. J., Sherwen, T., Jacob, D. J., Schmidt, J., Kinnison, D., Lamarque, J.-F., Apel, E. C., Bresch, J. C., Campos, T., Flocke, F. M., Hall, S. R., Honomichl, S. B., Hornbrook, R., Jensen, J. B., Lueb, R., Montzka, D. D., Pan, L. L., Reeves, J. M., Schauffler, S. M., Ullmann, K., Weinheimer, A. J., Atlas, E. L., Donets, V., Navarro, M. A., Riemer, D., Blake, N. J., Chen, D., Huey, L. G., Tanner, D. J., Hanisco, T. F., and Wolfe, G. M.: BrO and Bry profiles over the Western Pacific: Relevance of Inorganic Bromine Sources and a Bry Minimum in the Aged Tropical Tropopause Layer, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-572, in review, 2017.
Theodore K. Koenig et al.
Theodore K. Koenig et al.
Theodore K. Koenig et al.

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Short summary
We measured bromine monoxide from an aircraft. Total gas phase inorganic bromine (Bry) was inferred in a chemical box model constrained by in situ data. Bry significantly impacts human health and climate. Comparisons with global models show sea-salt is an important Bry source. We discovered a gas phase Bry minimum in the uppermost troposphere and hypothesize missing Bry partitions to aerosol. Multiphase bromine observations are needed to test this hypothesis and improve global models.
We measured bromine monoxide from an aircraft. Total gas phase inorganic bromine (Bry) was...
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