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Model Representation of Secondary Organic Aerosol in CMAQ v4.7
Citation:
CARLTON, A. G., P. BHAVE, S. NAPELENOK, E. O. EDNEY, G. SARWAR, R. W. PINDER, G. POULIOT, AND M. HOUYOUX. Model Representation of Secondary Organic Aerosol in CMAQ v4.7. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 44(22):8553-8560, (2010).
Impact/Purpose:
The National Exposure Research Laboratory′s (NERL′s) Atmospheric Modeling and Analysis Division (AMAD) conducts research in support of EPA′s mission to protect human health and the environment. AMAD′s research program is engaged in developing and evaluating predictive atmospheric models on all spatial and temporal scales for forecasting the Nation′s air quality and for assessing changes in air quality and air pollutant exposures, as affected by changes in ecosystem management and regulatory decisions. AMAD is responsible for providing a sound scientific and technical basis for regulatory policies based on air quality models to improve ambient air quality. The models developed by AMAD are being used by EPA, NOAA, and the air pollution community in understanding and forecasting not only the magnitude of the air pollution problem, but also in developing emission control policies and regulations for air quality improvements.
Description:
Numerous scientific upgrades to the representation of secondary organic aerosol (SOA) are incorporated into the Community Multiscale Air Quality (CMAQ) modeling system. Additions include several recently identified SOA precursors: benzene, isoprene, and sesquiterpenes; and pathways: in-cloud oxidation of glyoxal and methylglyoxal, particle-phase oligomerization, and acid enhancement of isoprene SOA. NOx dependent aromatic SOA yields are also added along with new empirical measurements of the enthalpies of vaporization and organic mass-to-carbon ratios. For the first time, these SOA precursors, pathways and empirical parameters are included simultaneously in an air quality model for an annual simulation spanning the continental U.S. Comparisons of CMAQ modeled secondary organic carbon (OCsec) with semiempirical estimates screened from 165 routine monitoring sites across the U.S. indicate the new SOA module substantially improves model performance. The most notable improvement occurs in the central and southeastern U.S. where the regionally averaged temporal correlations (r) between modeled and semiempirical OCsec increase from -0.5 to 0.8 and -0.3 to 0.8, respectively, when the new SOA module is employed. Wintertime OCsec results improve in all regions of the continental U.S. and the seasonal and regional patterns of biogenic SOA are better represented.
URLs/Downloads:
Model Representation of Secondary Organic Aerosol in CMAQ v4.7 (PDF, NA pp, 277 KB, about PDF)Environmental Science and Technology
Model Representation of Secondary Organic Aerosol in CMAQ v4.7 (PDF, NA pp, 539 KB, about PDF)