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MODELING PHOTOCHEMISTRY AND AEROSOL FORMATION IN POINT SOURCE PLUMES WITH THE CMAQ PLUME-IN-GRID
Citation:
GODOWITCH, J. M. AND J. O. YOUNG. MODELING PHOTOCHEMISTRY AND AEROSOL FORMATION IN POINT SOURCE PLUMES WITH THE CMAQ PLUME-IN-GRID. Presented at 7th Conference on Atmospheric Chemistry American Meteorological Society, San Diego, CA, January 09 - 13, 2005.
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:
Emissions of nitrogen oxides and sulfur oxides from the tall stacks of major point sources are important precursors of a variety of photochemical oxidants and secondary aerosol species. Plumes released from point sources exhibit rather limited dimensions and their growth is gradual, being strongly governed by meteorological dispersion processes. However, in the typical regional Eulerian grid modeling framework, a point source plume is actually a subgrid scale feature since grid cell sizes are generally 20 km or greater. On the other hand, plume widths do not generally achieve this horizontal dimension for a considerable distance/time after being emitted. Consequently, point source emissions are subjected to excessive dilution when instantly mixed into the entire grid cell volume when the traditional Eulerian grid modeling approach is applied. Therefore, a plume-in-grid (PinG) technique has been integrated into the state-of-science Community Multiscale Air Quality (CMAQ) chemical transport model to specifically provide a realistic treatment of the dynamic and chemical/aerosol processes impacting pollutant concentrations in major point source plumes.
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.