Consistent simulation of bromine chemistry from the marine boundary layer to the stratosphere – Part 1: Model description, sea salt aerosols and pH A. Kerkweg1,2, P. Jöckel1, A. Pozzer1, H. Tost1, R. Sander1, M. Schulz3, P. Stier4, E. Vignati5, J. Wilson5, and J. Lelieveld1 1MPI for Chemistry (Otto Hahn Institute), Atmospheric Chemistry Department, P.O. Box 3060, 55020 Mainz, Germany 2Institute for Atmospheric Physics, University of Mainz, Mainz, Germany 3Laboratoire des Sciences du Climat et de l'Environnement, CEA-IPSL, Saclay, France 4Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK 5Joint Research Centre, Institute of Environment and Sustainability, Ispra, Italy
Abstract. This is the first article of a series presenting a detailed analysis of
bromine chemistry simulated with the atmospheric chemistry general
circulation model ECHAM5/MESSy. Release from sea salt is an important bromine
source, hence the model explicitly calculates aerosol chemistry and phase
partitioning for coarse mode aerosol particles. Many processes including
chemical reaction rates are influenced by the particle size distribution, and
aerosol associated water strongly affects the aerosol pH. Knowledge of the
aerosol pH is important as it determines the aerosol chemistry, e.g., the
efficiency of sulphur oxidation and bromine release. Here, we focus on the
simulated sea salt aerosol size distribution and the coarse mode aerosol pH.
A comparison with available field data shows that the simulated aerosol
distributions agree reasonably well within the range of measurements. In
spite of the small number of aerosol pH measurements and the uncertainty in
its experimental determination, the simulated aerosol pH compares well with
the observations. The aerosol pH ranges from alkaline aerosol in areas of
strong production down to pH-values of 1 over regions of medium sea salt
production and high levels of gas phase acids, mostly polluted regions over
the oceans in the Northern Hemisphere.
Citation: Kerkweg, A., Jöckel, P., Pozzer, A., Tost, H., Sander, R., Schulz, M., Stier, P., Vignati, E., Wilson, J., and Lelieveld, J.: Consistent simulation of bromine chemistry from the marine boundary layer to the stratosphere – Part 1: Model description, sea salt aerosols and pH, Atmos. Chem. Phys., 8, 5899-5917, doi:10.5194/acp-8-5899-2008, 2008.