GDFILE

     GDFILE is the name of the file which contains gridded data.

     The input for GDFILE may contain more than one file name separated
     by +.  Up to three file names may be entered.  Individual operands
     in GFUNC or GVECT can be accessed from a specific file by placing
     +n after the operand name, where n is the number corresponding to
     the placement of the file name in the GDFILE input.  In the example
     below, the temperature from the third file is advected by winds
     from the first file:

		GDFILE = file1.grd + file2.grd + file3.grd
		GFUNC  = ADV ( TMPK+3, WND )
    
     The input for GDFILE may also be a file type.  The following file
     types are examples of the possible input. See the table,
     datatype.tbl, for the actual file types that can be used.

		NAM		NAM model grid
                GEFS            GFS ensemble
		GFS		GFS model grid
		RAP		Rapid update cycle
                SREF            Short Range Ensemble

      When one of these file types is input, the program searches
      locally for the most recent file first.  If no files are found
      locally, the program searches remotely for the most recent file.
      The remote directories are specified in the table, datatype.tbl.

      An optional base time may be included with the file type name,
      following a bar (|).  For example:

		GDFILE = nam | 00

      This will attempt to find the most recent run of the NAM
      model at 00Z.  The base time may be any valid format for a
      GEMPAK date/time.  Any missing parts of the date/time will be
      supplied by the last time.  If the entry in GDATTIM specifies
      a base time, that base time overrides the base time following
      the bar, which is ignored in that case.

      The entries in GDFILE are not required to have the same grid
      navigation.  The navigation of the internal grid on which
      computations are done is determined by the first GDFILE entry,
      the GAREA and PROJ inputs, and by IJSKIP input.  The latter
      three are used to determine a subset of the grid associated
      with the first GDFILE entry.  If the other GDFILE entries have
      different navigations, grids read from these files are remapped
      to the internal computational grid before any calculations
      are done.

      See the help for GRDHDR for an explanation of the grid header
      flags used for remapping.
      
      The members of an ensemble for ensemble diagnostic calculations
      are specified within a GDFILE entry by listing file names and 
      aliases, separated by commas and enclosed in curly brackets ({}).  
      Each alias therein may have an optional cycle time specification 
      appended to it following |.  The latest cycle time is the default.

      GDFILE input may have more than one ensemble specification among 
      its "+" separated entities.  If the first GDFILE entry is an 
      ensemble specification, then the internal grid is set using the 
      the first member in the ensemble specification.  This is an 
      important consideration when the members of the ensemble are on 
      different grids.

      The following is an example of a GDFILE entry containing an 
      ensemble specification:

	GDFILE = nam|06 + {sref,gfs|00,gfs|06,nam|06}

      In this example, the first entry is not an ensemble; while the 
      second is.

      The members of an ensemble may be assigned weights as percentages 
      ranging from 0 to 100.  The percentage is prefixed to the member 
      name and separated from it by a % character.  The sum of the 
      weights must not exceed 100.  If one or more members is not 
      assigned a weight, the residual between 100 and the sum of the 
      specified weights is divided equally among the members with no 
      weights assigned.  A weight preceding an alias representing 
      multiple members is divided equally among those members.  For 
      example, let GDFILE = { 72.5%ENS, 2.5%GFS, SREF, NAM }, where ENS
      has 11 members and SREF has 15 members.  Each of the 11 members 
      of ENS gets a weight of .06591, the GFS gets .025, and the SREF 
      and NAM share 25% so that each of the 15 members of SREF gets a 
      weight of .00833 and the NAM gets .125.  If no weights are given,
      all members are equally weighted.

      The individual members of an ensemble associated with an entry in
      the datatype.tbl file can be addressed by placing the individual
      member name following the name given in the first column of the
      datatype.tbl entry with a colon separator.  The member name is
      that character string for which the asterisk stands in the
      datatype.tbl entry.  For example, suppose the datatype.tbl entry
      is this:

      SRE $MM/sre sre_YYYYMMDDHH_*x CAT_GRD SCAT_FCT -1 -1 -1 OFF/0/0

      Suppose the four members associated with this template are:

      sre_YYYYMMDDHH_arw1x  sre_YYYYMMDDHH_arw2x  sre_YYYYMMDDHH_wrf1x
      sre_YYYYMMDDHH_wrf2x

      To use only the wrf1 model requires the following:

      GDFILE = sre:wrf1

      The arw sub-ensemble specification is this:

      GDFILE = {sre:arw1,sre:arw2}

      In each GDFILE entry, the name following the colon is the string
      for which the asterisk stands in the template of the datatype.tbl
      entry.

      Access to grid data in AWIPS database is accomplished by setting
      GDFILE to an alias found in datatype.tbl. Each entry for grid data
      references an XML control file that needs to be created to specify
      the attributes of the metadata in the database. For example, the 
      alias A2GFS uses the XML file $GEMTBL/data-access/gfs.xml.