9.4.3. Tips and recommendations - Chemical Mechanisms
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The versions of each chemical mechanism that include both aerosols and aqueous chemistry represent the most comprehensive
modeling approach.
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If you are neglecting or removing cloud processes, you can use the chemical mechanism that excludes the aqueous chemistry.
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You must use the same chemical mechanism for the CMAQ chemical transport model (CCTM) and all of the input processors that
are part of the CCTM system.
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The Euler Backward Iterative (EBI) chemistry solver is mechanism dependent. When you modify a chemical mechanism you will
not be able to use the default EBI solver for the new mechanism. The Rosenbrock and GEAR solvers are the only mechanism-independent
choices of chemistry solvers with the CCTM.
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When adding new species to CMAQ it is important to check that the sources of these new species into the modeling domain are
accounted for correctly in the mechanism include files. If you are adding these species to the domain through the emissions
files, the GC_EMIS.EXT include file must contain these new species. If the new species will also enter the domain as initial
and boundary conditions, check the GC_ICBC.EXT file for the presence of these species.