Reading GFS GRIB2 files: issues with gribmap

[Jennifer Adams]

On Jul 22, 2008, at 3:33 AM, Gilmour, Isla wrote:

> Using GrADS (v2.0.a2), wgrib2 (v1.7.7c) , g2ctl (v0.0.3h) and with
> perl
> installed, on UNIX (SunOS i386)
>
> Having downloaded grib2 GFS files of the form
> gfs.tccz.pgrb2.fxxx.grib2
> from NCEP
> (as described at http://www.nco.ncep.noaa.gov/pmb/products/gfs/ )
> I created a ctl file using g2ctl.  This looks relatively ok (see
> end of
> email for header), other than the tdef which is listed as 1mo rather
> than something more reasonable like 3h or 12h (the forecast leadtime
> varies from 3hrly 0-180h, then 12hrly out to 384h) so that's the
> second
> question... can GrADS ctl files deal with non-uniform time steps?
You need two descriptors, as Daniele described.
tdef 33 linear 00z22jul08 12hr
tdef 61 linear 00z22jul08 3hr

>
> Leaving tdef aside, the next step is to use gribmap (the one which
> comes
> with grads-2.0.a2) , but this failed:
>
>> g2ctl -0 /data/weather/gfs/20080714/00/gfs.t00z.pgrbf > gfs.ctl
>> gribmap -i gfs.ctl
> Open Error: Data file type invalid
> --> The invalid description file record is:
> --> dtype grib2
> The data file was not opened.
The 'dtype grib2' option should work with gribmap (the one that comes
with 2.0.a2). Please check your $PATH or use a complete path to
gribmap to make sure you're using the right one.

Jennifer

> Is there an alternative version of gribmap to use for GRIB2 files?
> Or a
> workaround which preserves the data in grib2 format?  (Or are these
> the
> "strange" gfs files mentioned in a previous thread?)
> Any help would be appreciated.
> Isla Gilmour
>
>  ----------------------------------------
>
> gfs.ctl header
>
> dset /data/weather/gfs/20080714/00/gfs.t00z.pgrbf84.grib2
> index /data/weather/gfs/20080714/00/gfs.t00z.pgrbf84.grib2.idx
> undef 9.999E+20
> title /data/weather/gfs/20080714/00/gfs.t00z.pgrbf84.grib2
> *  produced by g2ctl v0.0.3h
> * griddef=1:0:(360 x 181):grid_template=0: lat-lon grid:(360 x 181)
> units 1e-06 input WE:NS output WE:SN res 48 lat 90.000000 to
> -90.000000
> by 1.000000 lon 0.000000 to 359.000000 by 1.000000 #points=65160
>
> dtype grib2
> ydef 181 linear -90.000000 1
> xdef 360 linear 0.000000 1.000000
> tdef 1 linear 00Z14jul2008 1mo
> * PROFILE hPa
> zdef 26 levels 100000 97500 95000 92500 90000 85000 80000 75000 70000
> 65000 60000 55000 50000 45000 40000 35000 30000 25000 20000 15000
> 10000
> 7000 5000 3000 2000 1000
> options pascals
> vars 139
> [list of vars, which tally with wgrib2 listing]

--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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