19990909: help needed with converting grib files to GEMPAK format

Emily,

If the NetCDF files have a 2.5x2.5 degree grid spacing that is
constant, then that is a CED projection. If you can obtain those
files, I have a program called dcreanal that will dump the 
NetCDF reanalysis grids to gempak files. I included the dcreanal source
in the current gempak distribution - you can see in you have the
directory $NAWIPS/unidata/ldmbridge/dcreanal in your distribution,
or I can pack it up for you. It doesn't get built by default since
it requires you to have NetCDF built on your system already.

If you have the dcreanal directory, then to build:

set the NETCDF and NETCDFINC locations in $NAWIPS/config/Makeinc.common
for the location of the NetCDF library and include file on your system,
then
cd  $NAWIPS/unidata/ldmbridge/dcreanal
make clean
make all
make install
make clean

to run dcreanal:

dcreanal netcdf_file gemfile_YYMM.gem

The program using YYMM template will create monthly gempak files
from the netcdf input file.

Let me know if you need the dcreanal sourec (or its available
in the gempak patch level 12 distribution we currently provide).


Steve Chiswell
Unidata User Support



>From: Emily K Grover <address@hidden>
>Organization: .
>Keywords: 199909092030.OAA09294

>
>Steve,
>
>Thanks for the info. Another quick question: I think I can obtain the
>files in netCDF format. (They would have a 2.5 by 2.5 grid spacing.) Is is
>possible to convert files from netCDF to GEMPAK format? If so, what type
>of projecion would I indicate for the 2.5 x 2.5 grid spacing? Thanks again
>for your help.
>
>Emily
>_________________________________________________________________________
>Emily K. Grover                                        MMMMMM     MMMMMM
>University of Michigan                           MMMMM     MMMMM
>Atmospheric, Oceanic, and Space Sciences         MMMMMM   MMMMMM
>Mesoscale Meteorology Laboratory                 MMMMMMM MMMMMMM 
>734.764.0564                                     MMMM MMMMM MMMM
>                                                 MMMM  MMM  MMMM
>                                                MMMM       MMMM
>                                               MMMMMM     MMMMMM
>_________________________________________________________________________
>
>
>On Thu, 9 Sep 1999, Unidata Support wrote:
>
>> >From: Emily K Grover <address@hidden>
>> >Organization: .
>> >Keywords: 199909091906.NAA07311
>> 
>> >To whom it may concern,
>> >
>> >I am trying to convert reanalysis grib data files into GEMPAK format. I
>> >have tried both nagrib and dcgrib. I suspect that my problem lies with the
>> >grib file's projection. The reanalysis files have a Gaussian projection.
>> >As far as I can tell, GEMPAK doesn't have a Gaussian projection option in
>> >its tables. (If I am wrong, please correct me.) Below are the error
>> >messages I have received.
>> >
>> >
>> >When I use nagrib I receive the following error message:
>> >
>> >     [NAGRIB -10]  Input for GEMPAK output file is blank.
>> >
>> >When I use dcgrib I get the following error message:
>> >
>> >    Sep 09 18:30:08 dcgrib[6054]:  Invalid center id/grid 
>> >    id combination: 721948pres_msl.gem
>> >
>> >
>> >I have already confirmed that I have the proper directory structure and
>> >that I have version 5.4 gempak.
>> >
>> >Any help or suggestions you can offer will be greatly appreciated. Thank
>> >you in advance.
>> >
>> >Emily Grover
>> >
>> >_________________________________________________________________________
>> >Emily K. Grover                                     MMMMMM     MMMMMM
>> >University of Michigan                           MMMMM     MMMMM
>> >Atmospheric, Oceanic, and Space Sciences         MMMMMM   MMMMMM
>> >Mesoscale Meteorology Laboratory                 MMMMMMM MMMMMMM 
>> >734.764.0564                                     MMMM MMMMM MMMM
>> >                                                 MMMM  MMM  MMMM
>> >                                             MMMM       MMMM
>> >                                            MMMMMM     MMMMMM
>> >_________________________________________________________________________
>> >
>> >
>> >
>> 
>> 
>> Emily,
>> 
>> Your assumption is correct. GEMPAK is not capable of handling variable
>> spaced grids. The Gaussian grid format varies the grid row spacing
>> in the latitudinal direction. All of the Gempak grid functions expect
>> a rectangular grid.
>> 
>> In order to convert the data into Gempak format for display, you would need
>> to interpolate the data to a regularly spaced grid (eg CED projection).
>> 
>> Steve Chiswell
>> ****************************************************************************
>> Unidata User Support                                    UCAR Unidata Program
>> (303)497-8644                                                  P.O. Box 3000
>> address@hidden                                   Boulder, CO 80307
>> ----------------------------------------------------------------------------
>> Unidata WWW Service                        http://www.unidata.ucar.edu/     
>> ****************************************************************************
>> 
>