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

Table A-2 Explanation and Recommendations for the List of Key CALMET Model Options/Continued
Option Parameter Recommend
value
Explanation and Justification
Minimum distance between upper air station
This option is designed to avoid extrapolated surface data “competing” with
and surface station for which extrapolation of RMIN2
-1 actual upper air measurements when both surface and upper air
surface winds will be allowed
measurements are co-located. However, the better time resolution of the
surface data (hourly) suggests extrapolating may be appropriate. RMIN2
defined the distance between measurements defining “co-located”. Using -1
when IEXTRP = +/- 4 will ensure extrapolation of all surface stations
Gridded prognostic wind field model output
This option uses gridded prognostic meteorological model output as the
fields as initial guess wind field
IPROG
14 initial guess wind field in CALMET.
Time step (hours) of the prognostic model ISTEPPG 1 Usually this is an hourly time step. Some gridded prognostic data may be
input data
available only every 3 hours (ISTEPPG=3).
Use coarse CALMET fields as initial guess
Default is off (0), but useful option if you do not have prognostic model data.
fields
Radius of Influence Parameters
IGFMET 0 When switch is on (1) the coarse CALMET fields from an earlier run will be
used to define the IGF.
The recommended value is F which turns off the varying radius of influence
option. LVARY=T may be used when using objective analysis rather than
Use varying radius of influence
LVARY
F the diagnostic wind module (IWFCOD=0). LVARY=T results in the radius
of influence being expanded when no stations are within the fixed radius of
influence value. Caution is warranted because when LVARY=T, the model
effectively enlarges RMAX to incorporate the ‘nearest’ station regardless of
whether it is suitable or not.
Critical parameters and are discussed in the RMAX1
See Table 1-1 above
above table
Other Wind Field Input Parameters
RMAX2
RMAX3
-
Minimum radius of influence used in the RMIIN 0.1 Recommendation is a very small value (0.1 km). Used to prevent a divide by
wind field interpolation
zero error when a grid point and station are co-located.
Critical parameter and are discussed in the
above table
TERRAD - See Table 1-1 above
Critical parameters and are discussed in the
above table
R1, R2 - See Table 1-1 above
Relative weighting of the prognostic wind
Only change this value if CSUMM winds are used in the Step 1 wind field.
field
RPROG
0 CSUMM model data is very rarely used and outdated format of entering
prognostic wind speeds and direction into the model.
55