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A TEST OF THERMODYNAMIC EQUILIBRIUM MODELS AND 3-D AIR QUALITY MODELS FOR PREDICTIONS OF AEROSOL NO3-
Citation:
Yu, S., R L. Dennis, S J. Roselle, A. Nenes, J. Walker, B K. Eder, K L. Schere, J L. Swall, AND W. P. Robarge. A TEST OF THERMODYNAMIC EQUILIBRIUM MODELS AND 3-D AIR QUALITY MODELS FOR PREDICTIONS OF AEROSOL NO3-. Presented at 27th NATO/CCMS International Technical Meeting on Air Pollution Modeling and its Application, Banff, AB, CANADA, October 25 - 29, 2004.
Impact/Purpose:
The objectives of this task are to continuously develop and improve EPA's mesoscale (regional through urban scale) air quality simulation models, such as the Community Multiscale Air Quality (CMAQ) model, as air quality management and NAAQS implementation tools. CMAQ is a multiscale and multi-pollutant chemistry-transport model (CTM) that includes the necessary critical science process modules for atmospheric transport, deposition, cloud mixing, emissions, gas- and aqueous-phase chemical transformation processes, and aerosol dynamics and chemistry. To achieve the advances in CMAQ, research will be conducted to develop and test appropriate chemical and physical mechanisms, improve the accuracy of emissions and dry deposition algorithms, and to develop and improve state-of-the-science meteorology models and contributing process parameterizations.
Description:
The inorganic species of sulfate, nitrate and ammonium constitute a major fraction of atmospheric aerosols. The behavior of nitrate is one of the most intriguing aspects of inorganic atmospheric aerosols because particulate nitrate concentrations depend not only on the amount of gas phase nitric acid, but also on the availability of ammonia and sulfate, together with temperature and relative humidity. Particulate nitrate is produced mainly from the equilibrium reaction between two gas phase species, HNO3 and NH3.
It is a very challenging task to partition the semi-volatile inorganic aerosol components between the gas and aerosol phases correctly. The normalized mean error (NME) for predictions of nitrate is typically three times that for predictions of sulfate for a variety of 3 D air quality models applied to sections of the U.S. (Odman, et al., 2002; Pun, et al, 2004). For an annual average across the entire U.S. the NMEs of the predictions of nitrate from the U.S. EPA Models 3/Community Multiscale Air Quality Model (CMAQ) are two to three times larger than the NMEs for sulfate.
The research presented here was performed under the Memorandum of Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) and under agreement number DW13921548. Although it has been reviewed by EPA and NOAA and approved for publication, it does not necessarily reflect their policies or views.