DCGRIB2 (Unidata)

    DCGRIB2 decodes GRIB format grids from a real-time data
    feed, or from a file fed to the program through standard input, and
    writes the data to GEMPAK grid files.  The program is 
    controlled by inputs to the command line as well as several
    configuration tables.

    DCGRIB2 utilizes the GEMPAK GB library routines (as NAGRIB does)
    although several distinct features have been added to facilitate
    the use of the decoder with GRIB bulletins transmitted via
    NOAAPORT/FOS. 

    1. DCGRIB2 posses the capability to "stitch" together grids
       transmitted in tiles. Currently these grids are typically
       global grids, such as the "thinned" AVN, MRF, and ECMWF
       tiles. Since GRIB bulletins transmitted as tiles generally
       lack the projection information of the larger grid system
       of which the tile is imbedded, a lookup table 
       $GEMTBL/grid/dcgrib.tbl is maintained with this information.

    2. Ouput file name templates are supported using keys described below.

    3. If an output filename is not provided, the program will attempt
       to find a suitable template from the table $GEMTBL/grid/gribkey.tbl.
       By using this feature, a single dcgrib2 process may be invoked for
       many different sources of GRIB data (typically for real-time data).
       If a matching set of criteria exist, the grid is decoded. The first
       template that matches the search criteria will be used, such that
       global matches can be permitted. The number of grid entries in the
       output file can be set in the gribkey.tbl file.

    4. Up to MMFILE files will be opened at a time to allow for cycling of output
       files when different data sets are inter-mixed in the data stream.

           
    The command line inputs are program options, and the output_file name may
    use the defined template characters below. If the output_file name is ommited,
    a template in the gribkey.tbl file will be used if defined.

    For example, for real-time data feeds:
    
	dcgrib2 [options] [output_file]

    When using with the LDM, the GEMPAK grib routines must be able
    to access the grib tables located in the gempak distribution.
    This is done through the GEMTBL environmental variable.
    If the the LDM process does not have the GEMTBL variable set,
    then you must use the "-e GEMTBL=path" option.

    The following tables files are expected to be found:
	$GEMTBL/grid/cntrgrib[X].tbl
	$GEMTBL/grid/vcrdgrib[X].tbl
	$GEMTBL/grid/wmogrib[X].tbl
	$GEMTBL/grid/[CENTER]grib[X].tbl
	$GEMTBL/grid/dcgrib.tbl
	$GEMTBL/grid/gribkey.tbl

    If running the program interactively with standard input, 
    the input file must be also be specified.
    For example:
		
    dcgrib2 [options] [output_file] < input_file
    
    A template may be used to specify the output file name.  The file
    name template uses the date and time of the bulletin or report
    to replace the following characters.

	YYYY		Year with century
	YY		Year without the century
	MM		Month number
	DD		Day
	HH		Hour
	NN		Minute
	FF		Forecast hour (2 digit)
	FFF		Forecast hour (3 digit)
	###		Generating process model id (PDS Octet 5)
	@@@		Grid number (PDS Octet 7)
	%%%             Generating subcenter (PDS Octet 26)
	%subc%          replace with [CENTER]subcenter.tbl abbreviation for generating subcenter
	%ens%           replace with ensemble member extension

    Valid command line options for DCGRIB2 are:

	-v N, -m maxgrids, -d logfile, -t timeout, -h show help, -e PARM=value

    Other DC decoder options are ignored.

    In order to provide flexibility in decoded output. The following environmental
    variables may be used to configure the decoder:

	ENSEXT : Environmental variable for adding ensemble extensions to parameter names
		If ENSEXT is not set, use of PDSEXT parameter name extensions defaults 
		to yes for grib1 and no for grib2. If ENSEXT is set, and equal to 1, 
		then the extension will be added to parameter names. If ENSEXT is
		set, and not equal to 1, the PDS extension will not be added to parameter 
		names.

	MDMETH : Environmental variable for backward compatibility when decoding GRIB2 data.
		Default storage method uses GRIB2 packing (MDGRB2) for grib2 data, which is 
		not backward compatible with older GEMPAK distributions. If environmental 
		variable MDMETH=MDGDEC, use backward compatibility - which will be much 
		slower for GRIB2 decoding, and result in output files which may be much larger..