g2gdf.pl part2

[Eric Altshuler]

Hi Arlindo and Mark,

I have noticed something very strange about the gdf files that are generated for GFS files of type 'gfs.t??z.pgrb2bf??'. I have never used these particular GFS files and I'm not sure what they're for. (The 0.5 degree GFS grib-2 files I am familiar with are 'gfs.t??z.pgrb2f??'). In the gdf file, there are 37 pressure levels specified in the zdef line, every 25 mb from 1000 to 100 mb. However, the inventory reported by wgrib2 shows that: a) some fields are on multiple levels but not on all 37, b) some fields are on pressure levels (1, 2, 3, 5, 7 mb) that are not present in the zdef line. In the gdf file, all multilevel fields have "37,100" specified, even though most of them are NOT on all 37 levels, and different fields are available on different sets of levels (e.g. RHprs is at 875,825,...,125 mb -- only every 50 mb -- while SPFHprs is on all 37 levels specified in zdef, but ABSVprs is at 875,825,...,7,5,3,2,1 mb, which includes levels not specified in zdef). I have also found this behavior when running Wesley's g2ctl script on a linux system. It does not seem to make sense given the rules that grads uses for data descriptor files. For me, it may be a moot point because I don't use the 'pgrb2b' GFS files, but it's confusing to see this nonetheless. When I generate control files for the more familiar 'pgrb2' GFS files, everything appears as I would expect it to.

Eric

----- Original Message -----
From: "Arlindo da Silva" <dasilva at ALUM.MIT.EDU>
To: GRADSUSR at LIST.CINECA.IT
Sent: Tuesday, April 15, 2008 11:41:30 PM GMT -05:00 US/Canada Eastern
Subject: Re: g2gdf.pl part2

Mark,

  Please download g2gdf/g2ctl, .pl and .exe versions, from:

           http://opengrads.org/devel/win32/

  Then grab a gfs forecast, say


ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.2008041512/gfs.t12z.pgrb2bf06

and try this (.exe version):

g2gdf -verf gfs.t12z.pgrb2bf06

  I'd expect the attached .gdf/.inv files to be produced. Start grads and
type

ga-> g2_open gfs.t12z.pgrb2bf06.gdf
ga-> set lev 825
ga-> d g2(tmpprs)

  Does it work for you? The plot is attached. I tried this with Strawberry
perl, another native Win32 build:

  http://strawberryperl.com/

  The same should work with ActiveState perl. Let me know if it doesn't, and
I'll install it and give it a try. However, the .exe files were created with
Strawberry perl and should work as is --- no need for perl to be installed
on your machine at all.

  Good Luck,

     Arlindo


--
Arlindo da Silva
dasilva at alum.mit.edu