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PHOTOCHEMICAL SIMULATIONS OF POINT SOURCE EMISSIONS WITH THE MODELS-3 CMAQ PLUME-IN-GRID APPROACH
Citation:
Godowitch, J M. AND J O. Young. PHOTOCHEMICAL SIMULATIONS OF POINT SOURCE EMISSIONS WITH THE MODELS-3 CMAQ PLUME-IN-GRID APPROACH. Presented at 93 Annual Meeting of AWMA Conference, Salt Lake City, UT, June 18-22, 2000.
Impact/Purpose:
The objectives of this task are to continuously develop and improve the Community Multiscale Air Quality (CMAQ) modeling system, which is the science implementation within the Models-3 system framework for air quality simulation. 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. It relies on Models-3 I/O API to support machine independent data access and maintains simple interfaces among science processor modules to provide a high-level of modularity.
Description:
A plume-in-grid (PinG) approach has been designed to provide a realistic treatment for the simulation the dynamic and chemical processes impacting pollutant species in major point source plumes during a subgrid scale phase within an Eulerian grid modeling framework. The PinG science algorithms include a Plume Dynamics Model (PDM) processor and a Lagrangian plume module. The PDM processor generates plume dimensions and related parameters needed by the Lagrangian PinG module., which is an integral component of the Community Multiscale Air Quality (CMAQ) chemical transport model. PinG uses grid concentrations as boundary conditions and it provides an important feedback of plume pollutants to the grid in the appropriate grid cell when plume width reaches the grid cell size. Simulations were performed with the PinG treatment applied to point sources exhibiting a wide range of Nox emission rates situated in a regional modeling domain encompassing Nashville, Tennessee. Selected plume model results are presented from a case study day from Nashville/Middle Tennessee field study in June 1995. Modeled plume ozone and nitrogen species concentration evolved in the same manner found from observed plume data, which provides encouraging initial evidence of the capability of the PinG technique. The ozone recovery period in the modeled plume core and Nox oxidation were strongly dependent on the Nox emission rate. The excess ozone above background in the modeled plume was greater for point sources with higher Nox emissions.