Generic Guidance and Optimum Model Settings for the CALPUFF ...

2.3 Methodologies for Running CALMET
The CALPUFF modeling system can be run in several modes requiring different types of
meteorological data. The following lists three modes available to run CALMET and a fourth
mode using other meteorological processors.
1. CALMET No-Observations (No-Obs) Mode. CALMET using gridded numerical model
output (e.g., from the MM5, WRF, RAMS, RUC, Eta or TAPM models). No surface,
upper air or buoy observations are used in No-Obs mode.
2. CALMET Hybrid Mode. CALMET run using a combination of gridded numerical
meteorological data supplemented by surface and optional overwater buoy data.
3. CALMET Observations-Only (Obs) Mode. – CALMET using observed surface and
upper air data, plus optional buoy data.
4. Single meteorological station dataset. CALMET is not used but rather single station
meteorological data is passed directly into CALPUFF from a steady-state plume
processor. Examples of single station datasets are those used to drive the AERMOD,
AUSPLUME, CTDMPLUS or ISCST3 models. CALPUFF can be driven with any of
these meteorological datasets.
If good quality gridded prognostic meteorological data are available, CALMET No-Obs
mode is recommended as the preferred method for regulatory screening modeling. This
recommendation is based on the following factors: (a) No-Obs mode allows the important
benefits of the non-steady-state approach in CALPUFF to be included in the dispersion modeling
(e.g., spatially varying meteorology and dispersion, causality, recirculation, stagnation, pollutant
build-up, fumigation, etc.); (b) No-Obs mode makes use of three-dimensional, hourly prognostic
meteorological data often available at high resolution to drive CALMET and CALPUFF; (c) No-
Obs mode greatly simplifies the preparation of the CALMET inputs because a large number of
input variables dealing with observational data are not required and the difficulties of dealing
with potentially incomplete observational datasets are eliminated; (d) No-Obs mode provides a
relatively straightforward approach that facilitates agency review and approval of the
CALMET/CALPUFF simulations. The level of effort to run CALMET in No-Obs mode is
similar to that required to run the AERMOD terrain and meteorological processors (although the
output files will be much larger with CALMET). Depending on the results of the initial No-Obs
simulations, additional refinements can be made to the meteorological fields by adding
meteorological observations to CALMET.
Table 2-1 shows the differences in important CALMET model option switches between the “noobservations”
(No-Obs) simulation, vs. the hybrid prognostic observation approach, vs. the
observation-only approach. The variables in bold are site specific and care is needed in their
choices. All these variables are detailed in Appendix A. Each of the approaches is discussed
below.
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