Table of Contents - The Atmospheric Studies Group at TRC

Section 8: CALMET Model Files
range is specified to allow inclusion of multiple categories, for example "bay" and "ocean," in the
definition of the water body. To disable the overwater option, JWAT1 and JWAT2 are set to values
greater than the highest land use category listed in the GEO.DAT file. The default values of JWAT1 and
JWAT2 are both 999, indicating the overwater interpolation scheme is not applied in default mode.
Because the temperature of any grid cell whose land use is included in the range defined by JWAT1 and
JWAT2 will be determined by a weighting of all overwater data (SEA#.DAT files), it is recommended
that smaller or distant water bodies be assigned land use categories that are distinct from those used in
JWAT1 and JWAT2, to avoid use of inappropriate data in determining their surface temperatures. Thus a
small reservoir will have its temperature determined by surrounding land stations, rather than by ocean
buoy data. After viewing the initial temperature field that results from the CALMET run, the user may
wish to "fine tune" the fields using the extended, 52-class land use system in Table 8-7 and by altering the
land use assignments of particular grid cells or changing the land uses included in the JWAT1-JWAT2
range. For instance, by limiting the range to "ocean" only and then changing which near-shore cells are
considered to be "bay" and which are "ocean" the user can control the appearance of the temperature field
in the vicinity of the coastline.
The values of IWAT1 and IWAT2 (GEO.DAT Input File) are used to determine whether the overland or
overwater method will be used to produce a mixing height value for a particular grid cell. The default
values of IWAT1 and IWAT2 are both 55, restricting the overwater mixing height scheme to "large"
bodies of water. The user may change the values of IWAT1 and IWAT2 on a case-by-case basis to
include or exclude other water bodies from being considered as overwater. For instance, the user's
domain may have a bay where the mixing height should be determined using the overwater method but a
series of small lakes where the overland method would be more appropriate, so the "lake" category would
be excluded from the IWAT range. Alternatively, if one has a large lake that should be considered to be
"overwater" and a smaller lake that should be considered to be "overland", then the land use category for
the smaller lake could be changed to reflect some other category not in the IWAT range, such as forest or
wetland. It is recommended that if the user creates his or her own GEO.DAT fields for roughness length,
albedo, etc., they be weighted by the actual percentage of each land use in a given cell. That method is
more accurate and, if one subsequently changes the dominant land use category, the variables used to
calculate mixing height will still reflect the fact that there is water present in the grid cell.
The surface elevation data field is entered in "user units" along with a scaling factor to convert user units
to meters. The sample GEO.DAT file shown in Table 8-5 contains elevations in meters.
The gridded fields are entered with the 'NXM' values on a line. NXM is the number of grid cells in the X
direction. The data from left to right correspond to X=1 through NXM. The top line of a gridded field
correspond to Y=NYM, the next line to Y=NYM-1, etc. All of the GEO.DAT inputs are read in
FORTRAN free format. A detailed description of the GEO.DAT variables is contained in Table 8-8.
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