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

without regard to the scientific legitimacy of the options selected” (EPA, 2009a). The CALPUFF
working group noted that when running CALMET with prognostic meteorological model (e.g.,
WRF and MM5) output as input, the CALMET diagnostic effects and blending of meteorological
observations with the WRF/MM5 output degraded the WRF/MM5 meteorological fields. Thus,
the 2009 IWAQM Phase 2 Reassessment Report recommended CALMET settings with an
objective to try and “pass through” the WRF/MM5 meteorological model output as much as
possible for input into CALPUFF.
However, further testing of CALMET and CALPUFF by EPA’s CALPUFF workgroup found that the
recommended CALMET settings in the May 2009 IWAQM Phase 2 Reassessment Report did not
achieve the intended result to “pass through” the WRF/MM5 meteorological variables as
CALMET still re‐diagnosed some and modified other meteorological variables thereby degrading
the WRF/MM5 meteorological fields. Based in part of CALMET evaluations using tracer test
field study databases (presented in Appendix B of this report), EPA determined interim CALMET
settings that produced the best CALMET performance when compared to observed surface
winds and on August 31, 2009 released a Clarification Memorandum “Clarification on EPA‐FLM
Recommended Settings for CALMET” (EPA, 2009b) with new recommended settings for
CALMET. In the August 2009 Clarification Memorandum, EPA reiterated the desire to “pass
through” meteorology from the WRF/MM5 prognostic meteorological models to CALPUFF, but
the CALMET model at this time was incapable of achieving that objective.
In the meantime, EPA has developed the Mesoscale Model Interface (MMIF) software that
where possible directly converts prognostic meteorological output data from the MM5 or WRF
models to the parameters and formats required for direct input into the CALPUFF dispersion
model thereby bypassing CALMET. Version 1.0 of MMIF was developed in June 2009 (Emery
and Brashers, 2009) with versions 2.0 (Brashers and Emery, 2011) and 2.1 (Brashers and Emery,
2012) developed in, respectively, September 2011 and February 2012; we expect that MMIF
Version 2.1 will be publicly released in February 2012. MMIF specifically processes geophysical
and meteorological output files generated by the fifth generation mesoscale model (MM5) or
the Weather Research and Forecasting (WRF) model (Advanced Research WRF [ARW] core,
versions 2 and 3) and reformats the MM5/WRF output for input into CALPUFF..
The EPA CALPUFF workgroup has been evaluating CALPUFF using CALMET and MMIF
meteorological drivers using data from several historical tracer field studies. In addition to a
reevaluation of CALPUFF using CALMET and MMIF for the GP80 and SRL75 tracer studies that
were used in the 1998 EPA CALPUF tracer evaluation report (EPA, 1998a), the CALPUFF
workgroup has also evaluated CALPUFF using CALMET and MMIF meteorological drivers along
with 5 other LRT dispersion models for the 1983 Cross Appalachian Tracer Experiment
(CAPTEX). CALPUFF, along with four other LRT dispersion models, were also evaluated using
data from the 1994 European Tracer Experiment (ETEX).
1.2 PURPOSE
The purpose of this report is to document the evaluation of the CALPUFF LRT dispersion model
using data from four atmospheric tracer experiment field study databases. This includes the
comparison of the CALPUFF model performance using meteorological inputs based on the
CALMET and MMIF software and comparison of the CALPUFF model performance with other
LRT dispersion models.
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