Analysis of regional budgets of sulfur species modeled for the COSAM exercise |
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| Authors: | G J ROELOFS P KASIBHATLA L BARRIE D BERGMANN C BRIDGEMAN M CHIN J CHRISTENSEN R EASTER J FEICHTER A JEUKEN E KJELLSTRÖM D KOCH C LAND U LOHMANN P RASCH |
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| Institution: | Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Utrecht, The Netherlands;;Nicholas School of the Environment, Duke University, Durham, NC, USA;;Pacific Northwest National Laboratory, Richland, WA, USA;;Atmospheric Science Division, Lawrence Livermore National Lab, CA, USA;;Department of Chemistry, University of Cambridge, UK;;NASA Goddard Space Flight Center, Greenbelt, MD, USA;;National Environmental Research Institute, Roskilde, Denmark;;Pacific Northwest National Laboratory, Richland, WA, USA;;Max Planck Institute for Meteorology, Hamburg, Germany;;Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands;;Department of Meteorology, Stockholm University, Sweden;;NASA/GISS, New York, NY, USA;;Atmospheric Science Program, Dalhousie University, Halifax, Canada;;National Center for Atmospheric Research (NCAR), Boulder, CO, USA |
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| Abstract: | The COSAM intercomparison exercise (comparison of large‐scale sulfur models) was organized to compare and evaluate the performance of global sulfur cycle models. Eleven models participated, and from these models the simulated surface concentrations, vertical profiles and budget terms were submitted. This study focuses on simulated budget terms for the sources and sinks of SO2 and sulfate in three polluted regions in the Northern Hemisphere, i.e., eastern North America, Europe, and Southeast Asia. Qualitatively, features of the sulfur cycle are modeled quite consistently between models, such as the relative importance of dry deposition as a removal mechanism for SO2, the importance of aqueous phase oxidation over gas phase oxidation for SO2, and the importance of wet over dry deposition for removal of sulfate aerosol. Quantitatively, however, models may show large differences, especially for cloud‐related processes, i.e., aqueous phase oxidation of SO2 and sulfate wet deposition. In some cases a specific behavior can be related to the treatment of oxidants for aqueous phase SO2 oxidation, or the vertical resolution applied in models. Generally, however, the differences between models appear to be related to simulated cloud (micro‐)physics and distributions, whereas differences in vertical transport efficiencies related to convection play an additional rôle. The estimated sulfur column burdens, lifetimes and export budgets vary between models by about a factor of 2 or 3. It can be expected that uncertainties in related effects which are derived from global sulfur model calculations, such as direct and indirect climate forcing estimates by sulfate aerosol, are at least of similar magnitude. |
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