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Organic aerosol sources an partitioning in CMAQv5.2
Murphy, B., M. Woody, AND H. Pye. Organic aerosol sources an partitioning in CMAQv5.2. 2016 CMAS Conference, Chapel Hill, NC, October 24 - 26, 2016.
The National Exposure Research Laboratory (NERL) Computational Exposure Division (CED) develops and evaluates data, decision-support tools, and models to be applied to media-specific or receptor-specific problem areas. CED uses modeling-based approaches to characterize exposures, evaluate fate and transport, and support environmental diagnostics/forensics with input from multiple data sources. It also develops media- and receptor-specific models, process models, and decision support tools for use both within and outside of EPA.
We describe a major CMAQ update, available in version 5.2, which explicitly treats the semivolatile mass transfer of primary organic aerosol compounds, in agreement with available field and laboratory observations. Until this model release, CMAQ has considered these compounds to be nonvolatile, an assumption that has been shown to lead to inaccurate predictions of OA diurnal profiles during focused measurement campaigns. We also introduce an OA surrogate into the model, called Potential Combustion Secondary Organic Aerosol (pcSOA), which accounts for missing sources of primary organic vapor precursors to aerosol formation. These sources could include emissions of reactive intermediate volatility vapors, semivolatile vapor products that have been previously undetected in laboratory experiments (e.g. from sorption to chamber walls), and multigenerational aging of semivolatile vapors. We evaluate the new model against observations at several scales, showing noticeable improvement at single sites during short, 1-2 month simulations and slight improvement at regional/continental scales during annual simulations.
Record Details:Record Type: DOCUMENT (PRESENTATION/SLIDE)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
COMPUTATIONAL EXPOSURE DIVISION