Modeling atmospheric sulfur over the Northern Hemisphere during the Aerosol Characterization Experiment 2 experimental period

Carmen M. Benkovitz, Stephen E. Schwartz, Michael P. Jensen, Mark A. Miller, R. C. Easter, Timothy S. Bates

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22 Scopus citations


A high-resolution (1° × 1°, 27 vertical levels) Eulerian chemical transport and transformation model for sulfate, SO2, and related species driven by analyzed forecast meteorological data has been run for the Northern Hemisphere for June-July 1997 and extensively evaluated with observational data, mainly from air quality and precipitation chemistry networks. For ∼5000 evaluations, 50% of the modeled sulfate 24-hour mixing ratios were within a factor of 1.85 of the observations; 50% of ∼328 concurrent subgrid observations were within a factor of 1.33. Much greater subgrid variation for 24-hour SO2 mixing ratios (50% of ∼3552 observations, were within a factor of 2.32) reflects high variability of this primary species; for ∼12600 evaluations, 50% of modeled mixing ratios were within a factor of 2.54 of the observations. These results indicate that a substantial fraction of the modeled and observed differences is due to subgrid variation and/or measurement error. Sulfate mixing ratios are identified by source type (biogenic, volcanic, and anthropogenic) and production mechanism (primary and by gas-phase and aqueous-phase oxidation). Examination of key diagnostics showed substantial variation for the different types of sulfur, e.g., SO2 aqueous-phase oxidation rates of 29-102% d-1 and sulfate residence times of 4-9 days. Volcanic emissions contributed 10% of the sulfate burden and 6% of emissions, because the elevated release allows large fractional conversion of SO2 and long residence time. Biogenic SO2 was generally at lower concentrations than H2O2, resulting in efficient aqueous-phase oxidation; this source type contributed 13% of emissions but only 5% of sulfate burden. Anthropogenic sources were the dominant contributors to sulfur emissions (80%) and sulfate burden (84%).

Original languageEnglish (US)
Pages (from-to)1-28
Number of pages28
JournalJournal of Geophysical Research D: Atmospheres
Issue number22
StatePublished - Nov 27 2004
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology


  • CTM
  • Modelling
  • Sulfate


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