Improving Secondary Organic Aerosol (SOA) Models by Comparison to Chamber and Ambient Data and by Uncertainty and Sensitivity Analysis

This project will evaluate and compare models that predict the formation of secondary organic aerosol (SOA) in ambient air. SOA are formed in the atmosphere when gas-phase compounds, emitted from human activities and from plants, oxidize and condense into very small particles. These small particles may affect climate, air quality, and atmospheric visibility. Improved modeling of SOA formation will lead to improvements in air quality and climate models.

This research has three primary objectives: (1) to conduct inter-comparisons of different SOA models and test them against atmospheric relevant laboratory measurements and atmospheric measurements; (2) to do a rigorous uncertainty analysis of the models so that the significance of model-measurement differences can be understood; and (3) to perform a comprehensive sensitivity analysis to explore the influential model configurations and/or parameters for the model results of interest, such as aerosol mass and oxygen to carbon ratio. measurements. Several chemical mechanisms of SOA formation will be considered, including an explicit gas-phase inorganic chemistry and the reactions with the SOA precursors, continuous oxidation, gas-to-particle partitioning, and heterogeneous and condensed-phase reactions. Model performance will be evaluated by comparisons with laboratory measurements from the Potential Aerosol Mass (PAM) chambers at both Boston College and the environmental chamber at the California Institute of Technology, and by comparisons with ambient field data collected during the Southern Oxidant & Aerosol Study (SOAS), at a site located in a heavily forested area in Centreville, AL during June and July in 2013.