Re: question on lat/lon grid nav parameters... (fwd)

• To: bit-bucket <bit-bucket@xxxxxxxxxxxxxxxx>
• Subject: Re: question on lat/lon grid nav parameters... (fwd)
• From: Robb Kambic <rkambic@xxxxxxxxxxxxxxxx>
• Date: Fri, 21 May 1999 16:24:20 -0600 (MDT)

==============================================================================
Robb Kambic                                Unidata Program Center
Software Engineer III                      Univ. Corp for Atmospheric Research
rkambic@xxxxxxxxxxxxxxxx                   WWW: http://www.unidata.ucar.edu/
==============================================================================

---------- Forwarded message ----------
Date: Tue, 13 Apr 1999 09:40:29 -0500
From: Tom Whittaker <tomw@xxxxxxxxxxxxx>
To: Steve Chiswell <chiz@xxxxxxxxxxxxxxxx>
Subject: Re: question on lat/lon grid nav parameters...

Chiz:

Thanks for your note.  It sounds to me, then, that the 'avn-x'
grids are
"made up".  I would hope, though, that we could stick with the
GRIB definitions of the nav parameters; in this case then Lo2
should have a value of "330" (the longitude of the "last grid
point") rather than "240".

In understand from Don that Robb is working from home, so I'll
wait until he has access to the GRIB document.  For now, I'm just
computing the correct "end longitude" value.

tom

Steve Chiswell wrote:

Tom,

Robb is the cdl person, so I'll let him deal with the values
within the cdf file.

The avn-x file is created from 8 separate quasi-thinned octants.
These are the WMO headers H.[I-P]... KWB.
Grids I-P are the 8 octants. Thinned grids have the number
of row points decrease with the cosine of latitude to compensate
for the convergence of the meridians at the pole. The decoders
we have allow the user to specify the  resolution at which
the grids are stored since they must be thickened to a
rectangular grid.

The nominal resolution of the thinned grids is 1.25x1.25 degrees.
-30 Longitude is the nominal longitude of the left edge.
Each octant should cover 90x90 degrees (4 tiles in each hemisphere).

Steve

On Mon, 12 Apr 1999, Tom Whittaker wrote:

> Sorry, but I don't know which of you to write to about this.  One
> of the lat/lon
> grids that Don gave me as a sample, 99022512_avn-x.nc by name,
> has 73x73 rows and columns, a spacing of 5.0,2.5, and a beginning
> Longitude (value of "Lo1") of -30.
>
> The value for "Lo2" in the file is 240.  I would have expected a
> value of 330.
> This is the only sample lat/lon grid he gave me that's not from
> -180,180 so I don't know if this is a fluke or a problem.
> Or...if I just don't understand what the value of "Lo2" is
> supposed to be...?
>
> Thanks.
>
> tom
>
> --
> Tom Whittaker (tomw@xxxxxxxxxxxxx)
> University of Wisconsin-Madison
> Space Science and Engineering Center
> Phone/VoiceMail: 608/262-2759
> Fax: 608/263-6738
>

--
Tom Whittaker (tomw@xxxxxxxxxxxxx)
University of Wisconsin-Madison
Space Science and Engineering Center
Phone/VoiceMail: 608/262-2759
Fax: 608/263-6738