Table of Contents - The Atmospheric Studies Group at TRC

Section 9: CALPUFF
variable dispersion and stability conditions over multiple hours of transport will result even when using
the single-station meteorological data. However, in general, the preferred mode for most applications of
CALPUFF is to use the spatially variable fields generated by CALMET.
The minimum data required in the ISCMET.DAT file includes time-varying values of the vector flow
direction, wind speed, temperature, stability class, and mixing height (urban or rural), which are found in
the "base" ISC3 format. In addition, if dry or wet deposition are being modeled, or if turbulence-based
dispersion coefficients are to be computed based on micrometeorological parameters, time-varying values
of the surface friction velocity (u * ), Monin-Obukhov length (L), a time-varying surface roughness length
(z o ), precipitation rate, and precipitation type code are entered on an extended record. These additional
variables are contained in the augmented ISC3 meteorological file. If chemical transformation is being
modeled, time-varying values of short-wave solar radiation and relative humidity can also be included in
the extended record. In addition, time-varying values of the potential temperature lapse rate (d/dz) and
power law profile exponent (p) can be entered. Non-missing values of the basic meteorological variables
(i.e., vector wind direction, wind speed, temperature, stability class, and mixing height) must be provided
for all applications. The data fields for the extended record variables (u * , L, etc.) may be left blank if the
CALPUFF options are set so that they are not needed (e.g., no wet or dry deposition, no chemical
transformation, no computation of turbulence-based dispersion coefficients). However, if the CALPUFF
model options are set to require them, the model assumes that valid values of the extended record
variables will be provided for every period. The only exceptions are d/dz and p, which can be entered
for some periods and not others. If values of d/dz or p are missing (i.e., blank) for a given period, the
model will use its default or user-specified stability-dependent values (see the PLX0 and PTG0 variables
in Input Group 12 of the control file).
Sample ISCMET.DAT files are shown in Tables 9-6(a-c). Part (a) of the table shows the "base" ISC3
meteorological data record. The fully extended data record is shown in Part (b) of the table, and the form
of the extended record data with sub-hourly time steps is shown in Part (c). Table 9-7 lists the contents of
the ISCMET.DAT header records, and Table 9-8 describes the data records. Note that neither version of
the fully extended data record formats is produced by any available processing program. These formats
are defined here for those users who wish to transform non-standard data sources into a single-station
format file for use in CALPUFF.
Other data associated with the meteorological data in ISCMET.DAT are provided in the CALPUFF.INP
control file. These data include the anemometer height, surface roughness length, land use type,
elevation, and leaf area index of the modeling region. The anemometer height is required in the vertical
power law extrapolation of the wind speed. The roughness length is used if turbulence-based dispersion
coefficients are selected, and in the calculation of dry deposition velocities, when the hourly value is
missing. The land use category is used to determine if urban or rural dispersion coefficients are
appropriate when the Pasquill-Gifford/McElroy-Pooler dispersion coefficients are used. Also see the
variables IURB1 and IURB2 in Input Group 12 of the control file. They define the range of land use
categories that are to be considered urban (i.e., if the value of the land use category in the ISCMET.DAT
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