Table of Contents - The Atmospheric Studies Group at TRC

Section 9: CALPUFF
9.2.3 PLMMET.DAT
In addition to the capability to use three-dimensional wind fields generated by CALMET, a single-station
meteorological file can also be used by CALPUFF as its source of meteorological data. One form of
single station data accepted by CALPUFF is the AUSPLUME (Lorimer, 1976) type of data file. The
standard AUSPLUME data file can be used without modification, although some CALPUFF options
require additional meteorological variables that must be added as part of an extended data record.
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
9.2.1). 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. In
single station mode, CALPUFF assigns the single value of each variable read from the PLMMET.DAT
file to all grid points, resulting in a spatially uniform gridded field. However, the model does not assume
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 singlestation
meteorological data. However, in general, the preferred mode for most applications of CALPUFF
is to use the spatially variable fields generated by CALMET.
The PLMMET.DAT file includes the basic hourly data required by CALPUFF, including the wind
direction, wind speed, temperature, stability class, and mixing height. Note that PLMMET.DAT uses
wind direction in the usual meteorological convention (i.e., winds from the west blowing toward the east
has a value of 270°), while ISCMET.DAT uses flow vector (i.e., winds from the west toward the east have
a vector direction of 90°). The PLMMET.DAT format also contains data for the horizontal component of
turbulence ( ). If both components of turbulence are available, they should be entered through the use
of the PROFILE.DAT data file (see Section 9.2.4). Also, CALPUFF contains several options for
modeling chemical transformation that do not involve the use of a decay constant.
The PLMMET.DAT format does not contain micrometeorological variables (the surface friction velocity
and Monin-Obukhov length), precipitation data, solar radiation, or relative humidity. The Monin-
Obukhov length is inferred from the stability class and the surface roughness length using the Golder
(1972) relations. The friction velocity can then be estimated from the surface-layer similarity wind
profile equation. The remaining variables must be added to the standard file in an exended data record.
These fields may remain blank if they are not needed for the CALPUFF options selected. Precipitation is
needed for wet deposition modeling, and the solar radiation and humidity data are needed for chemical
transformation calculations.
Sample PLMMET.DAT files are shown in Tables 9-9(a) and 9-9(b). Part (a) of the table shows the
standard AUSPLUME meteorological data record. The extended data record is shown in Part (b) of the
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