Table of Contents - The Atmospheric Studies Group at TRC

Section 8: CALMET Model Files
8.2 Geophysical Data File (GEO.DAT)
The GEO.DAT data file contains the geophysical data inputs required by the CALMET model. These
inputs include land use type, elevation, surface parameters (surface roughness, length, albedo, Bowen
ratio, soil heat flux parameter, and vegetation leaf area index) and anthropogenic heat flux. The land use
and elevation data are entered as gridded fields. The surface parameters and anthropogenic heat flux can
be entered either as gridded fields or computed from the land use data at each grid point. Default values
relating each of these parameters to land use are provided in the model.
A sample GEO.DAT file is shown in Table 8-5. The first line of the file identifies the file and its format
to CALMET. The second line provides the number of comment lines (character strings of up to 80
characters in length) to follow that are read but are not interpreted by the model. One of these may
typically contain a title to identify the data set. The next block of 5 to 6 lines contains map projection,
datum, and grid information such as the number of grid cells, grid spacing, and reference coordinates.
These variables define the mapping coordinates used for the modeling and are checked by CALMET for
consistency and compatibility with the CALMET control file inputs. Eight sets of flags and data records
follow for the land use, elevation, surface parameters, and anthropogenic heat flux data.
The default CALMET land use scheme is based on the U.S. Geological Survey (USGS) land use
classification system. The USGS primary land use categories are shown in Table 8-6. Two Level I
USGS categories (water and wetlands) are subdivided into subcategories. Along with the default
CALMET land use, the default values of the other geophysical parameters for each land use type are also
shown. The default land use classification scheme contains 14 land use types. Note that a negative value
of land use by CALMET is used as a flag to indicate irrigated land. Irrigated land may be assigned a
different Bowen ratio than unirrigated land, and the CALPUFF dry deposition module uses the irrigated
land use flag in computing the effect of moisture stress on stomatal resistance. (If the land is irrigated, it
is assumed that the vegetation is not moisture stressed.)
CALMET allows a more detailed breakdown of land use or a totally different classification scheme to be
used by providing the option for user-defined land use categories. Currently, up to 52 user-specified land
use categories are allowed. An extended 52-class land use scheme based on the USGS Level I and Level
II land use categories is shown in Table 8-7. The user can specify up to "MXLU" land use categories
along with new values of the other geophysical parameters for each land use type. The parameter MXLU
is specified in the CALMET parameter file (PARAMS.MET).
CALMET contains an option, in which temperatures over water bodies such as the ocean or large lakes
are calculated by using data from only those observation stations (SEA.DAT files, usually buoys) located
in it, while only land stations (SURF.DAT file) will be used to calculate temperatures over the rest of the
grid. The variables JWAT1 and JWAT2 in CALMET.INP Input Group #6 specify the range of land use
categories defining the water body for which this land/water temperature scheme will be implemented. A
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