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

Table A-3 Explanation and Recommendations for the Overwater Surface Fluxes Switches/Continued
Option Parameter Recommended
value in typical
conditions
Explanation and Justification
Spatial Averaging of Mixing IAVEZI 1 Conduct spatial averaging which is recommended to smooth mixing heights
Heights
between grid cells
Maximum search radius in
Typical value is several (1-10) km, but must be expressed in terms of number of
averaging process (in grid cells) MNMDAV 1 grid cell grid cells (MNMDAV = X km/DGRIDKM). Note, default value of 1 cell is not
the recommended value. MNMDAV must be computed (in grid cell units) from
the search radius in km divided by the grid cell size (km)
Half-angle of upwind looking cone
for averaging
Layer of winds used in upwind
HAFANG 30 deg Default value based on model testing
averaging
ILEVZI
1
Default value based on model testing.
Convective
Options
Mixing Height
Method to compute the convective
Maul-Carson for land and water cells. The recommendation reflects the recent
mixing height
Threshold buoyancy flux required
IMIXH
1
research findings of the study sponsored by the MMS. The US EPA default of
IMIXH=-1 (Maul-Carson mixing height for over land only and the OCD mixing
height overwater) is not recommended because it does not reflect the findings of
the MMS-sponsored model evaluation work.
to sustain convective mixing height
growth overland
THRESHL 0.0 W/m 3
Threshold buoyancy flux required
to sustain convective mixing height
growth overwater
THRESHW 0.05 W/m 3
Recommended value based on testing sponsored by MMS over the Gulf of
Other Mixing Height Variables
Mexico.
Minimum potential temperature
Based on empirical testing, do not change unless have data to prove otherwise
lapse rate in stable layer above the
current convective mixing height
DPTMIN 0.001 deg K/m
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