Modeling Aqueous Secondary Organic Aerosol Formation

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The objective of this project is to develop a better understanding of chemical processes occurring in cloud droplets and wet atmospheric particles that can lead to the formation of secondary small particles in the atmosphere. A model will be applied to data collected in the field in 2013 during the Southern Oxidant and Aerosol Study to evaluate the fate of natural emissions to the atmosphere. This research effort will improve the understanding of factors that influence the formation of small particles through processing in cloud droplets and aerosol liquid water, hence leading to improved models of atmospheric chemistry, air quality and climate.State-of-the-art modeling approaches will be used to evaluate the formation of aqueous Secondary Organic Aerosol (aqSOA) and their impacts on aerosol mass, composition, and optical properties. Aqueous processing allows SOA formation from highly volatile species, including oxidation products of isoprene, such as glyoxal and isoprene epoxydiols (IEPOX). A photochemical box model, Gas-Aerosol Model for Mechanism Analysis (GAMMA) and its simplified version (simpleGAMMA), will be applied to analyses of field data using limited gas-phase tracer inputs. SimpleGAMMA was developed to be computationally efficient and suitable for coupling with larger-scale atmospheric chemistry models.A detailed intercomparison will be conducted of the SimpleGAMMA aqueous aerosol SOA formation scheme and other SOA formation schemes, such as the IEPOX SOA scheme from the Community Multi-scale Air Quality (CMAQ) model. The PI will also introduce or update aqSOA formation schemes in several 3D regional and global models including GEOS-Chem, GISS ModelIE2 Earth System Model, and WRF-Chem. This work will result in improved prognostic capabilities for atmospheric chemistry models.