Interpreting Aerosol Sources and Seasonality over the Southeast United States with the GEOS-Chem Model: Lessons from the SEAC4rs Campaign
Wednesday, 17 December 2014: 3:25 PM
The factors driving the aerosol seasonal cycle in the Southeast United States is an open problem in atmospheric chemistry. Satellite studies show strong seasonality of aerosol optical depth (AOD) peaking in summer and collocated with biogenic emissions, suggesting strong organic aerosol (OA) influence. In contrast, surface station measurements show a weaker seasonal cycle, primarily driven by sulfate. Previous studies have attempted to reconcile this apparent disconnect between the satellite and surface data by hypothesizing various sources of aerosol aloft. Here we interpret data from the SEAC4RS aircraft campaign in 2013, together with EPA AQS surface station measurements and MODIS and AERONET AOD, in a high-resolution version of the GEOS-Chem chemical transport model (CTM) with detailed ozone-aerosol chemistry. We use the aircraft observations to examine the consistency between the satellite and surface aerosol data. We quantify the contributions of anthropogenic, biogenic, and open fire sources to the different aerosol species, and examine relationships between species and their precursors as constraints on emissions and chemistry. This provides new insights on the factors that control aerosol concentrations, seasonality, and long-term trends in the Southeast US.