GDGSFC computes grid data and interpolates to stations in a
GEMPAK surface file.

INPUT PARAMETERS
 
    GDFILE    Grid file
    GDATTIM   Grid date/time
    GVCORD    Grid vertical coordinate
    GLEVEL    Grid level
    GFUNC     Scalar grid
    SCALE     Scalar scale / vector scale
    SFFILE    Surface data file
    SFPARM    Surface parameter list
 
 

PROGRAM DESCRIPTION
 
    This program interpolates computed grid data to stations
    in a GEMPAK surface file.

    The program computes the requested grid data from the given
    grid file.  GFUNC can be any valid GEMPAK grid function.  The
    other grid related parameters are used to specify the grid
    to calculate.

    The output surface file, SFFILE, must already exist.  The
    output parameter, SFPARM, must also exist in the surface file.
    The program reads each successive station from the surface file
    and overwrites the existing data with the interpolated data from
    the grid.


EXAMPLES
 
   1.  Read the surface temperature in Celsius from the 12 hour
       forecast from the latest ETA model and interpolate the
       values to the stations in the surface file new.sfc. The
       scaling fator is defaulted to 0.

       GDFILE  = eta
       GDATTIM = f12
       GVCORD  = none
       GLEVEL  = 0
       GFUNC   = tmpc
       SCALE   =
       SFFILE  = new.sfc
       SFPARM  = tmpc


   2.  Read the 500 mb vorticity from the 24 hour forecast from the
       latest GFS model and interpolate the values to the stations
       in the surface file vort.sfc with the scaling factor equal
       to 5.

       GDFILE  = gfs
       GDATTIM = f24
       GVCORD  = pres
       GLEVEL  = 500
       GFUNC   = vor(wnd)
       SCALE   = 5
       SFFILE  = vort.sfc
       SFPARM  = v500


ERROR MESSAGES
 
    [GDGSFC  -1]    Fatal error initializing TAE.
    [GDGSFC  -2]    Fatal error reading TAE parameters.
    [GDGSFC  -3]    Fatal error initializing GEMPLT.
    [GDGSFC  -4]    Cannot find SFPARM "..." in this surface file.