Documentation of the Evaluation of CALPUFF and Other Long ...

B.2 CONCLUSIONS OF CTEX3 CALMET SENSITIVITY TESTS
The evaluation of the CALMET modeling system using the CTEX3 field experiment database is
not a true independent evaluation because some of the surface meteorological observations
used as the evaluation database are also used as input into CALMET. Thus, care should be
taken in the interpretation of the CALMET meteorological model evaluation. In fact, EPA has
demonstrated that CALMET’s blending of meteorological observations with MM5 prognostic
meteorological model fields can actually produce unrealistic results in the wind fields (e.g.,
discontinuities around the wind observation sites) at the same time as improving the CALMET
statistical model performance at the meteorological monitoring sites.
Given these caveats, when looking at the alternative CALMET settings for RMAX1/RMAX2 the
CALMET configuration that best matches observed winds is with the 100/200 RMAX1/RMAX2
setting as recommended in the 2009 Clarification Memorandum. Other recommended settings
in the 2009 Clarification Memorandum (e.g., use of prognostic meteorological data as the initial
first guess wind field) are supported by the CALMET CTEX3 model evaluation. Note that better
wind field comparisons using the 2009 Clarification Memorandum recommended settings for
RMAX1/RMAX2 was also seen for the CTEX5 CALMET evaluation presented in Appendix A.
Although the CALMET meteorological model performance evaluation for alternative model
settings support the recommended 100/200 CALMET settings for RMAX1/RMAX2 in the
Clarification Memorandum, the evaluation of the CALPUFF/CALMET modeling system for the
CTEX3 and CTEX5 field experiments against observed tracer data presented in Chapter 5 come
to an alternative conclusion. The CALPUFF/CALMET evaluation against the observed tracer
observations in the CTEX3 and CTEX5 experiments found that different RMAX1/RMAX2
configurations produced better CALPUFF/CALMET tracer model performance for the two
CAPTEX experiments, but that the 100/200 recommended setting always produced the worst
CALPUFF/CALMET model performance. Given the large differences in the in the rankings of the
ability of the CALPUFF to reproduce the observed tracer concentrations across the different
meteorological model configurations in the two CAPTEX field experiments, it is unclear whether
a third experiment would produce another set of rankings.
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