SFMOD moves selected surface data from an input surface file to an
output surface file.


INPUT PARAMETERS
 
    SFFILE    *Surface data file
    SFOUTF    *Output surface file
    DATTIM    *Date/time
    AREA      *Data area
 
 
PROGRAM DESCRIPTION
 
    SFMOD takes data from an existing GEMPAK surface file,
    SFFILE, and writes the data into another existing surface
    file, SFOUTF.  This program can be used to subset the
    original dataset by time and/or stations.

    This program will not create a new surface file.  The GEMPAK
    program, SFCFIL, can be used to create a surface file.  If the
    parameters in the output file are not the same as the
    parameters in the input file, the required parameter
    conversions will be done.

    If a requested station or time is not in the output file, it
    will be added to the file if there is room.  The number of
    times and stations that can be included in a file is specified
    by TIMSTN in SFCFIL.


EXAMPLES
 
    1.  Put the data for all stations at the latest time in file
        TEST.SFC into a file called LAST.SFC.

        SFFILE  =  test.sfc
        SFOUTF  =  last.sfc
        DATTIM  =  last
        AREA    =  dset

    2.  Put the data for stations in Maryland and Virginia for
        all times into the output data set.

        SFFILE  =  test.sfc
        SFOUTF  =  last.sfc
        DATTIM  =  all
        AREA    =  @md/@va


ERROR MESSAGES
 
    [SFMOD  +3]     Some stations were not added to file.
    [SFMOD  +2]     Character parameter cannot be used:  ...
    [SFMOD  +1]     Parameter ... cannot be calculated.
    [SFMOD  -1]     Fatal error initializing TAE.
    [SFMOD  -2]     Fatal error reading TAE parameters.
    [SFMOD  -3]     There are no parameters to be computed.
    [SFMOD  -4]     Time ... cannot be added.