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19990727: Using NAGRIB to convert GRIB file to GEMPAK file

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  • Subject: 19990727: Using NAGRIB to convert GRIB file to GEMPAK file
  • Date: Tue, 27 Jul 1999 12:36:08 -0600
>From: Li-Chuan Chen <address@hidden>
>Organization: Iowa Institute of Hydraulic Research
>Keywords: 199907271524.JAA28895

>Dear Sir,
>
>       I tried to use NAGRIB to conver an Eta model output GRIB file which I
>obtain from the COMET web (96071712f12_eta.grib) to a GEMPAK file, but I
>didn't succeed.  The error message (NAGRIB 3 & -11) said the program
>can't find the valid parameter and open GEMPAK grid file.  Do you know
>what' wrong?  Could you give me an example about how to use NAGRIB in
>GEMPAK 5.2 and how to set up the values for the variables (for example:
>INDXFL, KXKY,MAXGRD and so on), or where I can find some reference?
>
>       Thanks for your assistance.
>
>-- 
>
>
>Li     
>
>*****************************************
>Li-Chuan Chen
>
>Iowa Institute of Hydraulic Research
>The University of Iowa
>300 S. Riverside Dr.
>Iowa City, IA52242
>
>tel: (319)335-6168
>fax: (319)335-5238
>e-mail: address@hidden
>http://www.icaen.uiowa.edu/~lchen
>*****************************************
>

Li,

The current version of Gempak we support is Gempak 5.4. Its possible that
iether you don't have the GEMTBL environmental variable set in your 
environment, or that the parameters in use for the model identifiers
during the time of your data set (1996) were not available when Gempak 5.2
was produced.

To run NAGRIB, check that $GEMTBL in your csh environment is pointing
to the gempak tables directory. In Gempak 5.4, the general way to decode
a grib file using the grib GDS to create the output file is:

GBFILE   = 96071712f12_eta.grib
INDXFL   = 
GDOUTF   = 96071712_eta.gem
PROJ     =
GRDAREA  = 
KXKY     =
MAXGRD   = 2000
CPYFIL   = gds
GAREA    =
OUTPUT   =
GBTBLS   =
GBDIAG   =
GEMPAK-NAGRIB> r



Using CPYFIL=gds will allow nagrib to determing the projection and garea
information from the grib data itself. MAXGRD defines the amount of space
to be set asside for grids in the Gempak file. In this case, we would have
space for 2000 grids to be written.

When NAGRIB is run, it uses the tables in $GEMTBL to define the vertical
coordinates, parameters, and model center. These must be found, so you
should double check all your Gempak environmental variable settings.

Steve Chiswell