gribmap(1)              GrADS  V1.6.beta4              gribmap(1)

NAME
     gribmap - "maps" between the GRIB and the GrADS descriptor.

SYNOPSIS
     gribmap [-i fname] [-v] [-t0] [-0] [-sxxxxx] [-hxxx] [-fxxx]

DESCRIPTION
     gribmap is a GrADS utility that "maps" between GRIB data and
     the GrADS data description.

     When you set up a GrADS data  descriptor  file  (e.g.,   the
     ".ctl" file), you are defining, external to the data itself,
     a structure, - how many variables, how times in a  file  (or
     set  of  files with the template option), the spatial dimen-
     sion or "shape" of the  variables,  etc.  The  GrADS  format
     (floats, either 64-bit or 32-bit IEEE depending on platform)
     is so simple that the relationship between the  data  struc-
     ture  defined  in  the .ctl file is calculated and stored in
     memory when the file is opened.

     What makes GRIB so painful is that there is NO  relationship
     between  the  GRIB  data  and  the bigger structural context
     implied by the .ctl file. Hence,  the  need  for  a  utility
     which  "maps"  between  the  GRIB  data  and  the GrADS data
     description.

     How this actually happens in gribmap is that each  field  in
     the  GRIB  data  file  is read and its parameters (variable,
     level, time, etc.) are extracted and  compared  to  ALL  the
     variables  at  any of the level/times/UNITS in the .ctl file
     until a match is found.

     The new features of gribmap allow restrictions to be  placed
     on  this matching process.  gribmap supports GRIB0 and GRIB1
     format (version 0 and version 1).

     Second the code now automatically scans for character string
     "GRIB"  vice  having  to  worry  about  headers and what not
     (e.g., "junk" between the beginning and the end of the  GRIB
     message).  That  is unless you are NMC and put (duh) GRIB in
     the header.  The default scan limit is  1000  which  can  be
     changed via the command line option.

OPTIONS
     -i fname       fname is the input grib file name.

     -v             nicer output to verify what you are  attempt-
                    ing to map.

     -t0            a match can only occur if the  base  time  in
                    the  grib  record  is the same as the initial
                    time in the .ctl file. This is used  to  pull

GrADS  V1.6.beta4         Last change:                          1

gribmap(1)              GrADS  V1.6.beta4              gribmap(1)

                    out a forecast sequence (0, 12, 24, .., 72 h)
                    starting a specific time (e.g., 95010300).

     -0             ignore the forecast time in  setting  up  the
                    match.  This  is  useful  in reanalysis where
                    some of the diagnostic fields are "valid"  at
                    slightly  different forecast time even though
                    they share the same starting time.

     -sxxxxx.       where xxxxx is the max  number  of  bytes  to
                    search between records for GRIB.

     -hxxx          bypass the bytes  before  starting  the  scan
                    process; where xxx is the number of bytes, or
                    for NMC:  -hnmc

     -fxxx          where xxx is the forecast time in  hours.  In
                    this  case,  a match occurs only if the fore-
                    cast time in  the  grib  record  matches  xxx
                    (hours).  This  is used to isolate a sequence
                    of forecasts, e.g., all the 120  h  forecasts
                    verifying  during  the  period 00z1jan1995 to
                    12z2jan1995 from the MRF ensemble runs.

EXAMPLES
     Here is a nice trick. To verify what is  mapped  during  the
     gribmap:
           gribmap -v -t0 ..... | grep MATCH
          all records MATCH matching will be displayed.

SEE ALSO
     grads(1), gribscan(1)
     - GrADS Documentation V1.5.1.12 (gadoc151.ps),
          Brian Doty (COLA), Mike Fiorino (LLNL), Tom Holt (UEA)
     - GrADS commands and scripting language reference cards,
          Karin Meier (DKRZ)

GrADS  V1.6.beta4         Last change:                          2