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

Table 3‐4. CALMET Parameters July 8, 1980 GP80 experiment, 1998 and current 600 km
analysis.
CALMET
Option Description
Maximum search radius for averaging
MNDAV mixing heights (# grid cells)
ZIMIN Minimum overland mixing height (in
meters)
ZIMAX Maximum overland mixing height (in
meters)
RMIN Minimum radius of influence in wind
field interpolation (in km)
1998 EPA
Setup
25
BASE
Setup
3 1
100 50
3200 3000
2.0 0.1
3.2.1.2 CALPUFF Control Options
The following CALPUFF control parameters, which are a subset of the control parameters, were
used. These parameters and options were mostly chosen to be consistent with the 1977 INEL
study (Irwin 1997) and 1998 EPA CALPUFF evaluation (EPA, 1998a) studies. This includes the
use of the slug option (MSLUG = 1) for the 100 km arc CALPUFF simulations. The use of the slug
option is very non‐standard for LRT modeling and inconsistent with the EPA‐FLM
recommendations for far‐field CALPUFF modeling. As stated on the CALPUFF website 18 :
“A slug is simply an elongated puff. For most CALPUFF applications, the modeling of
emissions as puffs is adequate. The selection of puffs produces very similar results as
compared to the slug option, while resulting in significantly faster computer runtimes.
However, there are some cases where the slug option may be preferred. One such case
is the episodic time‐varying emissions, e.g., an accidental release scenario. Another case
would be where transport from the source to receptors of interest is very short (possibly
involving sub‐hourly transport times). These cases generally involve demonstration of
causality effects due to specific events in the near‐ to intermediate‐field.”
For the farther out 600 km arc, the slug option was not selected (MSLUG = 0) for the initial
CALPUFF sensitivity tests even through the slug option was used in the 1997 INEL and 1998 EPA
studies. However, we did investigate the use of the slug option, as well as puff splitting, in a set
of additional CALPUFF sensitivity tests for the 600 km arc.
CALPUFF options for technical options (group 2):
MCTADJ = 0 No terrain adjustment
MCTSG = 0 No subgrid scale complex terrain is modeled
MSLUG = 1 For 100 km BASE case near‐field puffs modeled as slugs
MSLUG = 0 For 600 km BASE case modeled as puffs (i.e., no slugs)
MTRANS = 1 Transitional plume rise is modeled
MTIP = 1 Stack tip downwash is modeled
MSHEAR = 0 100 km BASE case – Vertical wind shear is NOT modeled above
stack top
= 1 600km BASE case
MSPLIT = 0 No puff splitting
18 http://www.src.com/calpuff/FAQ‐answers.htm