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

B.1 CALMET MODEL EVALUATION TO IDENTIFY RECOMMENDED CONFIGURATION
The CAPTEX Release #3 (CTEX3) meteorological database was used to evaluate different
configurations of the CALMET meteorological model for the purposes of helping to identify a
recommended configuration for regulatory far‐field CALMET/CALPUFF modeling. The results
from these CALMET CTEX3 sensitivity tests were used in part to define the recommended
CALMET model options in the August 31, 2009 Memorandum from the EPA/OAQPS Air Quality
Modeling Group “Clarifications on EPA‐FLM Recommended Settings for CALMET (i.e., the 2009
Clarification Memorandum). The EPA Clarification Memorandum on CALMET settings (EPA,
2009a) was a follow‐up to a draft May 27, 2009 document: “Reassessment of the Interagency
Workgroup on Air Quality Modeling (IWAQM) Phase 2 Summary Report: Revisions to Phase 2
Recommendations” (EPA, 2009a). The IWAQM Phase 2 Reassessment Report recommended
settings for CALMET that were intended to facilitate the direct “pass through” of prognostic
meteorological model (e.g., MM5 and WRF) output to CALPUFF as much as possible. However,
in subsequent testing of the new recommended CALMET settings in the IWAQM Phase 2
Reassessment Report using the CTEX3 database, the performance of CALMET degraded
compared to some other settings. This led to the August 31, 2009 Clarification Memorandum
of recommended CALMET settings for regulatory far‐field modeling.
EPA examined 31 different configurations of the CALMET diagnostic meteorological model
using the CTEX3 database. The resultant CALMET wind fields were paired in space and time
with observations using the CALMETSTAT tool. CALMETSTAT is an adaptation of the METSTAT
program that is typically used to evaluate the MM5 and WRF prognostic meteorological models
against surface meteorological observations.
Note that since CALMET uses some of the same meteorological observations as input as used in
the evaluation database, this is not a true evaluation as by design CALMET’s STEP2 objective
analysis (OA) will modify the wind field to make the winds better match the observations at the
locations of the monitoring sites. But as noted by EPA (2009a,b), this can be at the expense of
degrading the wind fields.
Table B‐1 lists the 31 CALMET sensitivity tests that were performed using the CTEX3 modeling
database. These CALMET sensitivity tests differed in the following aspects:
• The resolution of the CALMET gridded fields (18, 12 and 4 km);
• The resolution of the MM5 prognostic meteorological model output used as input to
CALMET (80, 36 and 12 km);
• How the MM5 data was used in CALMET (i.e., as a first guess field prior to the STEP 1
diagnostic effects, as the STEP 1 wind fields prior to STEP 2 blending (objective analysis or
OA) of observations or the MM5 data are not used at all); and
• Whether the surface and upper‐air meteorological observations were used (NOOBS=0) or
not (NOOBS=2).
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