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

Table A-1 An Explanation of the 7 Critical User-Defined, Site Specific Parameters When Using Observational Data in CALMET/ Cont……
Option Parameter Recommended Value Explanation and Justification
Requires user input. Value R2 represents the comparable distance for winds in layers 2
in km specific to each and above. It is important to note that all the results of the
model domain
diagnostic wind model (kinematics, slope and blocking
1 value represents all effects) are contained in the Step 1 wind field, thus if too
stations
much weight is given to the observations, then you will
essentially erase all the information generated in creating
Not used in No-Obs model the Step 1 winds. Rule of thumb is to start with small R1
and R2 values and slowly increase these values if you do
not believe the surface stations are showing enough weight.
Typically for observation sites in flat terrain values of R1
and R2 are larger than in mountainous terrain where a
station’s flow is limited by the valley segment.
The values of RMAX are also used in the construction of
Maximum radius of influence for RMAX1 No Default
the Step 2 wind field, where the observed winds are
meteorological stations in layer 1 (Step and
'blended' in with the Step 1 winds. Any observation for
2) and layers aloft (Step2)
RMAX2 Requires user input. Value which Rk (the distance from the grid cell to the k-the
in km specific to each observation location) is greater than RMAX1 in the surface
model domain
layer, or RMAX2 aloft is excluded from the above
1 value represents all 'blending' formula. We can use RMAX1 and RMAX2 to
stations
exclude observations from being inappropriately included
(as they are in the next valley, on the other side of a
Not used in No-Obs model mountain, etc.). Note, if you are using RMAX1 and
RMAX2 to exclude observations, then you do not want to
set LVARY to T, as then CALMET will increase the
values of RMAX1 and RMAX2 to at least capture the
nearest observation, regardless of whether this makes
sense.
Typically values of RMAX1 and RMAX2 are smaller than
R1 and R2, this way ‘sharp’ boundaries between the Step 1
wind field and the weighted observation station are
prevented.
*1 IEXTRP - affects vertical extrapolation of surface winds,and whether layer 1 data from upper air stations are ignored, and is normally is set to -4. Setting IEXTRP < 0, means
that the lowest layer of the upper-air observation will not be considered in any interpolations. Since upper-air observations are only taken every 12-hours, the time-interpolated
surface wind values from the upper-air observations are usually of no use. When IEXTRP is set to -4, similarity theory is used to extrapolate the surface winds into the layers aloft,
which provides more information on observed local effects to the upper layers. Setting IEXTRP to 0 means that no vertical extrapolation from the surface wind data is used.
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