CALPUFF and Postprocessors

F.2.2
ISCMET.DAT
CALPUFF can be driven by a single-station standard ISC3-type of meteorological file, compatible with
the earlier ISC2 version of the model, or the augmented ISC3-type of meteorological file. In addition, the
ISCMET.DAT file used by CALPUFF can accommodate an extended data record that includes the
augmented ISC3 data plus variables not found in either a standard ISC3 data record, or the augmented
ISC3 data record. In the description to follow, we refer to the standard ISC3 file as the "base" ISC3
format.
CALPUFF is normally run with a full three-dimensional wind field and temperature field, as well as twodimensional
fields of mixing heights and other meteorological variables (see CALMET.DAT in Section
F.2.1). However, in some near-field applications, when spatial variability of the meteorological fields
may not be significant (e.g., uniform terrain and land use), the single-station data file may be used. The
model uses the data in the ISCMET.DAT file to fill the 2-D or 3-D arrays with the scalar values read from
the file. In single-station mode, CALPUFF assigns the single value of each variable read from the
ISCMET.DAT file to all grid points, resulting in a spatially uniform gridded field. However, the model
does not assume that the meteorological conditions are steady-state, which allows the important effects of
causality to be simulated even with the single-station meteorological data. For example, the time required
for plume material to reach a receptor is accounted for in the puff formulation, and curved trajectories and
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 hourly 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, hourly 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, hourly values of short-wave solar radiation and relative humidity can also be included in the
extended record. In addition, hourly values of the potential temperature lapse rate (d2/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 hour. The only exceptions are d2/dz and p, which can be entered for
some hours and not others. If values of d2/dz or p are missing (i.e., blank) for a given hour, the model
will use its default or user-specified stability-dependent values (see the PLX0 and PTG0 variables in
MAR 2006 – CALPUFF
F-101