Table of Contents - The Atmospheric Studies Group at TRC

Section 8: CALMET Model Files
8.3 Upper Air Data Files (UP1.DAT, UP2.DAT,...)
The upper air data used by CALMET are read from upper air data files called UPn.dat, where n is the
upper air station number (n=1,2,3, etc.). The upper air data files can be created by the READ62
preprocessor program from standard NCDC upper air data formats or by application-specific
reformatting programs. Observations made at non-standard sounding times can be used by CALMET.
The UPn.DAT files are formatted, user-editable files containing at least five header records followed by
groups of data records. A sample upper air data file generated by READ62 and hand-edited to remove
informational messages and to fill in missing soundings is shown in Table 8-9. 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 line after all comment
records identifies the map projection for any locations provided in the file. Presently, the projection is
NONE as no locations are provided. The next record identifies the time zone of the data in the file, which
is typically UTC (e.g., the zone is UTC+0000). The next record contains the beginning and ending dates
of data contained in the file and the top pressure level of the sounding data. The last header record
contains the READ62 data processing options used in the creation of the file.
The data records consist of a one-record header listing the origin of the data (6201 for NCDC data or
9999 for non-NCDC data), station ID number, date and time, and information on the number of sounding
levels. Following this are the pressure, elevation, temperature, wind direction, and wind speed for each
sounding level. The format of the UPn.dat file is shown in Table 8-10.
As discussed in Section 3.0, the model allows missing values of wind speed, wind direction, and
temperature in the UP.DAT files at intermediate levels. The model will linearly interpolate between valid
levels to fill in the missing data. The user is cautioned against using soundings for which this
interpolation would be inappropriate. Missing soundings should be replaced with soundings for the same
time period from a representative substitute station. Each data set must be processed on a case-by-case
basis with careful consideration given to how to deal with missing data.
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