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Assessment of the Aerosol Optics Component of the Coupled WRF-CMAQ Model usingCARES Field Campaign data and a Single Column Model
Citation:
Gan, C., F. Binkowski, Jon Pleim, J. Xing, David-C Wong, R. Mathur, AND R. Gilliam. Assessment of the Aerosol Optics Component of the Coupled WRF-CMAQ Model usingCARES Field Campaign data and a Single Column Model. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 115:670-682, (2015).
Impact/Purpose:
The National Exposure Research Laboratory’s Atmospheric Modeling 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:
The Carbonaceous Aerosols and Radiative Effects Study (CARES), a field campaign held in central California in June 2010, provides a unique opportunity to assess the aerosol optics modeling component of the two-way coupled Weather Research and Forecasting (WRF) – Community Multiscale Air Quality (CMAQ) model. This campaign included comprehensive measurement of aerosol composition and optical properties at two ground sites and aloft from instrumentation on-board two aircraft. A single column model (SCM) was developed to evaluate the accuracy and consistency of the coupled model using both observation and model information. Two cases (June 14 and 24, 2010) are examined in this study. The two-way coupled model has been updated with several modifications such as densities and refractive indices for different particulate matter species based on Optical Properties of Aerosol and Clouds (OPAC) dataset and Mie and core-shell scattering/absorption approaches. The results show that though the coupled WRF-CMAQ estimates of aerosol extinction were underestimated relative to these measurements, when measured concentrations and characteristics of ambient aerosols were used as input to constrain the SCM calculations, the estimated extinction profiles agreed well with aircraft observations. A possible explanation is that the simulated sea-salt (SS) in accumulation mode in WRF-CMAQ is very low in both cases while the observations indicate a considerable amount of SS. Also, a significant amount of organic carbon (OC) is present in the measurement which is underestimated in the model calculation. Additionally, the treatment of the relative amounts of model estimated carbonaceous aerosol as water soluble in the optical calculations could also influence the estimated total extinction. In conclusion, the aerosol optics calculation is working well but the missing or insufficient species masses in the full coupled model simulation are the possible causes of the underestimated extinction. Improved SS emission modeling and revisions to more fully account for OC in the optical calculations are being pursued.
URLs/Downloads:
ORD-008980 SCM_REVISE_FINAL_FINALOCT21_2014.PDF (PDF, NA pp, 908.43 KB, about PDF)Atmospheric Environment
