Alternative small scale meteorology input to a chemical transport ...

easy to switch from one coordinate to another depending on the application. This way a single
CTM formulation can adapt to any of the coordinates commonly used in meteorological models.
Unlike a model with a fixed coordinate system, a generalized coordinate system allows use of
generic coordinates for the specific science processes within a model. That means each science
process can utilize the parameterizations based on the best coordinates to represent the
problem. For example, the planetary boundary layer (PBL) parameterizations can be expressed
in terms of geometric height, or dimensionless height scaled with PBL height, or in terms of
pressure for cloud physics.
The linkages between the generic coordinate parameterizations in the science processes
and the governing equations in the generalized coordinates are established through the
application of appropriate coordinate transformation rules. The derivation of the governing
equations in the generalized coordinates for the CMAQ and the assumptions for that derivation
are presented in detail in Chapter 6 of Byun et al., 1999.
Chemical transformations are another important part of the CMAQ system. In this study
ozone formation and distribution is used as a testing tool. Ozone is not emitted directly in the
atmosphere, but is formed through a set of photochemical reactions of nitric oxides (NOx) and
volatile organic compounds (VOCs) emitted by anthropogenic and natural sources. The sun
light provides the necessary energy to break the chemical bounds in the molecules and produce
atomic oxigen, which in turn reacts with molecular oxigen to form ozone. The photochemical
mechanism of ozone production and loss is quite complex and the reaction rates depend on
amount of solar radiation and air temperature.
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