Re: [idvusers] HOW TO : Plot views across the prime meridian using IDV

• To: webmaster-IWC <webmaster@xxxxxxxxxxxxxxxxxxxxxxxxxx>
• Subject: Re: [idvusers] HOW TO : Plot views across the prime meridian using IDV
• From: Don Murray <dmurray@xxxxxxxxxxxxxxxx>
• Date: Wed, 09 Jan 2008 12:47:50 -0700

Hi Ian-

Thanks for sharing this with the group.  This will be good for those
who want to subset the gridded datasets.

the first.  I just put out a new nightly build (2.5a1) that extends
the grid if need be so there is no longer a gap at the edge.  If
anyone wants to test that for me, I'd welcome feedback.  You can
download the latest nightly build from:

http://www.unidata.ucar.edu/downloads/idv

I've tested with the Global 2.5, 1.0 and .5 degree grids on our
UCAR server.

Don Murray

webmaster-IWC wrote:

Hi all,

OK I have managed to get around this problem with plotting across the

prime meridian - and it works, which did surprise me!
So I thought I would share how this can be done.

Data set

GFS global model 1x1 deg from NCEP

Software required

IDV (unidata | display)
Cnvgrib (NCO | convert grib 2 to grib 1)
Convsh + Subset.tcl (BADC | create regional subsets into NetCDF)

1. First download your data. You need to download the whole grid as

cnvgrib will not work with partial downloading of grib files
2. Use Cnvgrib to convert grib 2 files into grib 1 (Example cnvgrib -g21
gfs.t00z.pgrbf09.grib2 subset.grb)
3. Create a regional subset from the new grib 1 file data set (Example
convsh subset.tcl -i subset.grb -o subset.nc -xs -60 -xe 60 -xi 1 -ys 0
-ye 90 -yi 1)

The new subset file is now in NetCDF format with the starting grid lon @

-60, this fixes the problem that IDV has plotting across the meridian.

FOR XP USERS ONLY. I have complied copy of Cnvgrib.exe if any users require this. Other programs and documents needed can be found below: BADC

HYPERLINK
"http://badc.nerc.ac.uk/help/software/xconv/#utilites"http://badc.nerc.a
c.uk/help/software/xconv/#utilites
HYPERLINK
"http://badc.nerc.ac.uk/help/software/xconv/subset.html"http://badc.nerc
.ac.uk/help/software/xconv/subset.html

NCO

HYPERLINK
"http://www.nco.ncep.noaa.gov/pmb/codes/GRIB2/"http://www.nco.ncep.noaa.
gov/pmb/codes/GRIB2/

Good luck and have fun Ian

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--
*************************************************************
Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
*************************************************************

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