Atmospheric Sciences Modeling Division
Air Resources Laboratory
National Oceanic and Atmospheric Administration
Research Triangle Park, NC 27711, USA
*On assignment to the National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. USA.
Sources of meteorological data are diverse and many difficulties can arise while linking these with air quality models. To provide an integral view of meteorological and air quality modeling, a robust and fully compressible governing set of equations has been introduced with the Models-3 Community Multiscale Air Quality (CMAQ) modeling system. When the input meteorological data are recast with the proposed set of governing equations, chemical transport models can follow the dynamic and thermodynamic descriptions of the meteorological data closely. This allows linking of CMAQ to many different types of meteorological models. Also, it has been known that certain Eulerian numerical advection schemes for trace species suffer serious mass conservation problems when subject to realistic meteorological data. In particular, for cases in which meteorological data are not mass-consistent (i.e., density and wind fields do not exactly satisfy the continuity equation), this problem can grow out of bound for a long-term simulation of trace species transport. To mitigate this problem, several mass (air density) adjustment schemes have been applied to atmospheric models. In the presentation different mass adjustment schemes are compared for their numerical characteristics, such as preservation of constant mixing ratio fields, mass conservation, and effects on linearity of advection algorithms.
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