Re: WRF grib2 data

Hi Anthony-

Anthony P Praino wrote:

Thanks for your reply. If I understand correctly, following the NcmL example, I could create the file manually to combine the separate files into one and use IDV to read it in.

Yes.  Just open it in the Files chooser.  If you set the file extension
to ncml, it will read it in as gridded data, or you can set the
Data Source Type to be "Grid files (netCDF/GRIB/OPeNDAP)".

However, with IDV version 2.2, you can use the Files Data Chooser
to select several GRIB files and if you set the Data Source Type
to be Aggregated Grid files, the IDV will do the aggregation on the fly.
You can select multiple files from the Files Chooser using Ctrl-click.

What is not clear from your comments is whether this will or will not work with netCDF,

Probably not the WRF netCDF files, but you can try. ;-)  I don't have
any sample WRF netCDF datasets where the times are in separate files.

 if not will it work with grib files?

Yes, that's the case I showed and that we have tested.

Not having read the
updates, is this only possible in version 2.2?

The IDV has had the ability to read NcML files for a while, but there
may have been some fixes in the latest netCDF-Java release (2.2.20)
which might make it more reliable in IDV version 2.2.  The latest
netCDF-Java release is included with the IDV version 2.2.

BTW, I just announced the release of IDV 2.2.


No problem.

Don Murray <dmurray@xxxxxxxxxxxxxxxx> 05/11/2007 05:53 PM
Please respond to

Anthony P Praino/Watson/IBM@IBMUS
Re: WRF grib2 data

Hi Anthony-

Anthony P Praino wrote:
I assume this may be a newbie question but I have checked the user
tutorial and scanned archives but have not run across an answer.

Well, you didn't miss anything.  It's just not there.

How does
one 'catalog' or group gridded data files together. I am trying to
animation sequences of WRF gridded fields from a locally run model. When
use the data chooser to select a group of WRF output files which are timestepped files (either netCDF or grib2), I cannot group them in order

to create a display based upon a selected field of multiple times.

The nightly release of the IDV allows you to aggregate WRF
GRIB2 files together from disk or from a remote server. You can download this from:

 From disk, use the file chooser and set the Datasource Type to be
"Aggregated Grid files".   This will not work with the WRF netCDF files.
Basically, the grid reader generates a netCDF Markup Language (NcML) aggregation file on the fly. You could also just create an NcML file
manually and read that in.  For information on creating NcML files for
aggregation, see:

The NcML that the Aggregated Grid Data uses looks something like:

<netcdf xmlns="";>
<aggregation type="joinExisting" dimName="time">
<netcdf location="file:/I:/rtmodel/07051012_nmm_alt1.GrbF000" />
<netcdf location="file:/I:/rtmodel/07051012_nmm_alt1.GrbF001" />
<netcdf location="file:/I:/rtmodel/07051012_nmm_alt1.GrbF002" />

This is still not in the documentation, though. ;-)

I have
tried this with cataloged data sources and it works fine (what are the details of gridded catalog sources such as NCEP NAM 12km).

This has all timesteps in one file.

I have also
tried to manually create a display out for each time which I can see in the dashboard but the display visual does not change even though the
appear to be sequencing. Any help of pointers to such information is appreciated.

If there is only one time associated with the data, it gets shown on all
times. So, in this case, each file has one timestep and they all get shown no matter what time the animation is on.

We hope to make a full release of version 2.2 on Monday.

Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307

Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307