Re: 20040506: netCDF Decoders - Sun UNIX - CDLs

On Thu, 6 May 2004, Unidata Support wrote:

>
> ------- Forwarded Message
>
> >To: address@hidden
> >From: "Beth Hall" <address@hidden>
> >Subject: netCDF Decoders - Sun UNIX - CDLs
> >Organization: DRI
> >Keywords: 200405070023.i470NhxJ020678 netCDF decoders gribtonc CDL
>
> Institution: Desert Research Insitute
> Package Version: decoders-3.0.3
> Operating System: Sun UNIX
> Hardware Information: Sun
> Inquiry: I'm trying to access data from the ldm feed, partiticularly
> the GFS data.  I feel very lost, but finally found the gribtonc
> command.  I originally used the gfs_211.cdl file, but it gave me no
> lat/lon coordinates, just x and y.

Beth,

No lat/lon are given because of rounding errors, no accurate values. The
lat/lon are mainly for human information.



With this cdl, the ncdump -h said
> there were 21 records (I'm assuming this refers to the forecasts,
> themselves).

Your correct the records are for forcast times:

 valtime_offset = 0, 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78,
84, 90, 96, 102, 108, 114, 120 ;


 I did some web searching and found that there were other
> CDLs including a 1 degree CDL.

The 1 degree grids are only on the CONDUIT feed, not the standard NOAAPORT
feed.


  I tried it along with the
> gfs_21-24.cdl, gfs_25-26.cdl, and the gfs_37-44.cdl.  Several of those
> actually have the lat/lon coordinate information, but now show 0
> records (no forecast data?).

Maybe you don't have the correct pqact entries, here's the ones we are
using. Remember the white spaces are tabs between the parts of the
entries.

# GFS model on global 5.0 x 2.5 degree grids
HRS     ^H.[A-D]... .... (..)(..).*/m(SPEC62MRF|MRF)
        PIPE    /usr/local/ldm/decoders/gribtonc
        etc/gfs_21-24.cdl
        data/pub/decoded/netcdf/GRIB/(\1:yyyy)(\1:mm)\1\2_gfs_21-24.nc

# GFS model on global 5.0 x 5.0 degree grid
HRS     ^H.[EF]... KWB. (..)(..)
        PIPE    /usr/local/ldm/decoders/gribtonc
        etc/gfs_25-26.cdl
        data/pub/decoded/netcdf/GRIB/(\1:yyyy)(\1:mm)\1\2_gfs_25-26.nc


# GFS model on thinned grids, interpolated to global 5.0 x 2.5 regular
grid
HRS     ^H.[I-P]... KWB. (..)(..).*(/mAVN|/mSSIAVN)
        PIPE    /usr/local/ldm/decoders/gribtonc
        -q "lin,dlat=2.5,dlon=5.0" etc/gfs_37-44.cdl
        data/pub/decoded/netcdf/GRIB/(\1:yyyy)(\1:mm)\1\2_gfs_37-44.nc

I know the data must be there, but clearly
> don't understand what these different CDLs are doing, which one I

The cdl file are templates for making the NetCDF files, the number
designation at the end of the cdl refers to the grib sections ie 21-24
that are stitched together to form the whole grib file.

Robb...

> should use, and which ones give me the lat/lon coordinate information.
> Can you help?  Thanks.
>
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===============================================================================
Robb Kambic                                Unidata Program Center
Software Engineer III                      Univ. Corp for Atmospheric Research
address@hidden             WWW: http://www.unidata.ucar.edu/
===============================================================================