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

MPDF = 0 PDF NOT used for dispersion under convective conditions
MREG = 0 No check made to see if options conform to regulatory
Options
Two different values were used for the dispersion parameterization option MDISP:
= 2 Dispersion coefficients from internally calculated sigmas
= 3 PG dispersion coefficients for RURAL areas (PG)
In addition, under MDISP = 2 dispersion option, two different options were used for the
MCTURB option that defines the method used to compute turbulence sigma‐v and sigma‐w
using micrometeorological variables:
= 1 Standard CALPUFF routines (CAL)
= 2 AERMOD subroutines (AER)
Several miscellaneous dispersion and computational parameters (group 12) were set as follows:
SYTDEP = 550. Horizontal puff size beyond which Heffter equations are
used for sigma‐y and sigma‐z
MHFTSZ = 0 Do NOT use Heffter equation for sigma‐z
XMXLEN = 1 Maximum length of slug (in grid cells)
XSAMLEN = 1 Maximum travel distance of puff/slug (in grid cells) during one
sampling step
MXNEW = 99 Maximum number of slugs/puffs released during one time step
WSCALM = 0.5 Minimum wind speed (m/s) for non‐calm conditions
XMAXZI = 3000 Maximum mixing height (meters)
XMINZI = 50 Minimum mixing height (meters)
SL2PF = 10 Slug‐to‐puff transition criterion factor (= sigma‐y/slug length)
A review of the respective CALPUFF parameters between the 1998 EPA CALMET/CALPUFF
evaluation study using CALMET Version 4.0 and the BASE case scenario in the current
CALMET/CALPUFF evaluation using CALPUFF Version 5.8 indicates differences in some
parameters. The differences between the two scenarios are presented below in Table 4‐4. All
other major CALPUFF options for current BASE case scenario matched the original 1998 EPA
analysis.
59