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

ACURATE: The Atlantic Coast Unique Regional Atmospheric Tracer Experiment (ACURATE)
operating during 1982‐1983 and consisted of measuring Krypton 85 air concentrations from
emissions out of the Savannah River Plant in South Carolina (Heffter et al., 1984). 12‐ and
24‐hour average samples were collected for 19 months at five monitoring sites that were
300 to 1,000 km from the release point.
ANATEX: The Across North America Tracer Experiment (ANATEX) consisted of 65 releases
of three types of Perflurocarbon Tracers (PFTs) that were released from Glasgow,
Montana and St. Cloud, Minnesota over three months (January‐March, 1987). The PFTs
were measured at 75 monitoring sites covering the eastern U.S. and southeastern Canada
(Draxler and Heffter, Eds, 1989).
CAPTEX: The Cross Appalachian Tracer Experiment (CAPTEX) occurred during September
and October, 1983 and consisted of 4 PFT releases from Dayton, Ohio and 2 PFT releases
from Sudbury, Ontario, Canada (Ferber et al., 1986). Sampling occurred at 84 sites from
300 to 800 km from the PFT release sites.
INEL74: The Idaho National Engineering Laboratory (INEL74) experiment consisted of
releases of Krypton 85 during February‐March, 1974 with sampling taken at 11 sites
approximately 1,500 km downwind stretching from Oklahoma City to Minneapolis (Ferber
et al., 1977; Draxler, 1982).
GP80: The 1980 Oklahoma City Great Plains (GP80) consisted of two releases of PFTs on
July 8 and July 11, 1980. The first PFT release was sampled at two arcs at a distance 100
km and 600 km with 10 and 35 monitoring sites on each arc, respectively (Ferber et al.,
1981). The second PFT release was only monitored at a distance of 100 km at the
corresponding 10 sites from the July 8 release.
The DATEM website also includes a model evaluation protocol for evaluating LRT dispersion
models using tracer field experiment that was designed following the procedures by Mosca et
al. (1998) for the ATMES‐II study and Stohl et al., (1998). The DATEM model evaluation
protocol has four broad categories of model evaluation:
1. Scatter among paired measured and calculated values;
2. Bias of the calculations in terms of over‐ and under‐predictions;
3. Spatial distribution of the calculation relative to the measurements; and
4. Differences in the distribution of unpaired measured and calculated values.
A recommended set of statistical performance measures are provided along with a FORTRAN
program (statmain) to calculate them. The DATEM recommendations have been adopted in
this study and more details on the DATEM recommended ATMES‐II model evaluation approach
is provided in section 2.4.3.
2.4 MODEL PERFORMANCE EVALUATION APROACHES AND METHODS
2.4.1 Model Evaluation Philosophy
To date, no specific guidance has been developed by the USEPA for evaluating LRT models.
According to EPA’s Interim Procedures for Evaluating Air Quality Models (Revised), the rationale
for selecting a particular data group combination depends upon the objective of the
performance evaluation. For this it is necessary to translate the regulatory purposes of the
intended use of the model into performance evaluation objectives (EPA, 1984; Britter, et al.,
1995). Under the approach for both the 1986 and 1998 EPA LRT model evaluation projects, no
particular emphasis was placed on any data group combination or set of statistical measures.
13