Atmos. Chem. Phys. Discuss., 12, 31205-31245, 2012
www.atmos-chem-phys-discuss.net/12/31205/2012/
doi:10.5194/acpd-12-31205-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Impact of the marine atmospheric boundary layer on VSLS abundances in the eastern tropical and subtropical North Atlantic Ocean
S. Fuhlbrügge1, K. Krüger1, B. Quack1, E. Atlas2, H. Hepach1, and F. Ziska1
1GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, Germany
2Rosenstiel School for Marine and Atmospheric Sciences, Miami, Florida

Abstract. During the DRIVE ("Diurnal and Regional Variability of Halogen Emissions") ship campaign we investigated the variability of the halogenated very short-lived substances (VSLS) bromoform (CHBr3), dibromomethane (CH2Br2) and methyl iodide (CH3I) in the marine atmospheric boundary layer in the eastern tropical and subtropical North Atlantic Ocean during May/June 2010. Highest VSLS mixing ratios were found near the Mauritanian coast and close to Lisbon (Portugal). Air mass origins were calculated with 5-day backward trajectories starting at the surface and at the boundary layer top. We identified predominantly air masses from the open North Atlantic with some coastal influence in the Mauritanian upwelling area, due to the prevailing NW winds. Maximum VSLS mixing ratios above the Mauritanian upwelling were 8.92 ppt for bromoform, 3.14 ppt for dibromomethane and 3.29 ppt for methyl iodide, with an observed maximum diurnal variability up to 50% for bromoform, 26% for dibromomethane and 56% for methyl iodide. A relationship was found between the marine atmospheric boundary layer (MABL) height and bromoform, dibromomethane and methyl iodide abundances. Lowest MABL heights above the Mauritanian upwelling area coincide with highest VSLS mixing ratios and vice versa above the open ocean. Significant high anti-correlations confirm this relationship for the whole cruise. We conclude that especially above oceanic upwelling systems MABL height variations are an important driver for VSLS mixing ratio variations and elevated atmospheric abundances and may explain the so far observed missing VSLS sources in this region.

Citation: Fuhlbrügge, S., Krüger, K., Quack, B., Atlas, E., Hepach, H., and Ziska, F.: Impact of the marine atmospheric boundary layer on VSLS abundances in the eastern tropical and subtropical North Atlantic Ocean, Atmos. Chem. Phys. Discuss., 12, 31205-31245, doi:10.5194/acpd-12-31205-2012, 2012.
 
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