Evaluation of GEOS-5 sulfur dioxide simulations during the Frostburg, MD 2010 field campaign

Abstract. Sulfur dioxide (SO 2 ) is a major atmospheric pollutant with a strong anthropogenic component mostly produced by the combustion of fossil fuel and other industrial activities. As a precursor of sulfate aerosols that affect climate, air quality, and human health, this gas needs to be monitored on a global scale. Global climate and chemistry models including aerosol processes along with their radiative effects are important tools for climate and air quality research. Validation of these models against in-situ and satellite measurements is essential to ascertain the credibility of these models and to guide model improvements. In this study, the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) module running on-line inside the Goddard Earth Observing System version 5 (GEOS-5) model is used to simulate aerosol and SO 2 concentrations. Data taken in November 2010 over Frostburg, Maryland during an SO 2 field campaign involving ground instrumentation and aircraft are used to evaluate GEOS-5 simulated SO 2 concentrations. Preliminary data analysis indicated the model overestimated surface SO 2 concentration, which motivated the examination of the specification of SO 2 anthropogenic emission rates. As a result of this analysis, a revision of anthropogenic emission inventories in GEOS-5 was implemented, and the vertical placement of SO 2 sources was updated. Results show that these revisions improve the model agreement with observations locally and in regions outside the area of this field campaign. In particular, we use the ground-based measurements collected by the United States Environmental Protection Agency (US EPA) for the year 2010 to evaluate the revised model simulations over North America.