Abstract:
The Community Multi-scale Air Quality (CMAQ) modeling system has been designed to approach air quality as a whole by including state-of-the-science capabilities for modeling multiple air quality issues, including tropospheric ozone, fine particles, toxics, acid deposition, and visibility degradation. In this way, the development of CMAQ involves the scientific expertise from each of these areas
... and combines the capabilities to enable a community modeling practice. CMAQ was also designed to have multi-scale capabilities so that separate models were not needed for urban and regional scale air quality modeling.
The CMAQ modeling system simulates various chemical and physical processes that are thought to be important for understanding atmospheric trace gas transformations and distributions. The CMAQ modeling system contains three types of modeling components: a meteorological modeling system for the description of atmospheric states and motions, emission models for man-made and natural emissions that are injected into the atmosphere, and a chemistry-transport modeling system for simulation of the chemical transformation and fate. CMAQ science code (updates) will be available via anonymous ftp.
The CMAQ consists of six interface processors:
* Meteorology-chemistry interface processor (MCIP)
* Photolysis rate processor (JPROC)
* Initial conditions processor (ICON)
* Boundary conditions processor (BCON)
* Chemical-transport model processor (CCTM)
The CMAQ modeling system was designed to have a flexible community modeling structure based on modular components. CMAQ CTM (CCTM) includes the following process modules:
* Horizontal advection
* Vertical advection
* Mass conservation adjustments for advection processes
* Horizontal diffusion
* Vertical diffusion
* Gas-phase chemical reaction solver
* Aqueous-phase reactions and cloud mixing
* Aerosol dynamics and size distributions
* Plume chemistry effects
* Aerosol deposition velocity estimation
* Photolytic rate computation
* Process analysis 
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