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[IDV #CLG-761846]: Re: [idvusers] Problem using NARR-A as aggregated GRIB files in IDV

Hi Ryan-

Sorry for the delay in responding.  I've been out for the past few
weeks.
 
> I seem to have come across the same problem as I've found on the message
> board (see below).  While I could use the "Make a time sequence" formula,
> this quickly becomes old when 20+ files are involved.  I'm using NCEP model
> data and have similar time tag issues... i.e.,
> 
> The "fnl_060913_00_00" file:
> 
> :_CoordinateModelRunDate = "2006-09-13T00:00:00Z"
> int time(time=1);
> :long_name = "forecast time";
> :units = "hour since 2006-09-13T00:00:00Z";
> :GRIB_orgReferenceTime = "2006-09-13T00:00:00Z";
> :GRIB2_significanceOfRTName = "Start of forecast";
> :_CoordinateAxisType = "Time";
> 
> 
> The "fnl_060913_06_00" file:
> :_CoordinateModelRunDate = "2006-09-13T06:00:00Z";
> int time(time=1);
> :long_name = "forecast time";
> :units = "hour since 2006-09-13T06:00:00Z";
> :GRIB_orgReferenceTime = "2006-09-13T06:00:00Z";
> :GRIB2_significanceOfRTName = "Start of forecast";
> :_CoordinateAxisType = "Time";
> 
> 
> I'm thinking that the easiest workaround would be to write a script to make
> all of the model run times to be the same while varying the
> orgReferenceTime.  Is this appropriate?   I'm open to tweaking the IDV code
> if that makes more sense.

The issue is down in the netCDF Java code and a fix is being worked on
for the next version.  But that release is several months away.  However,
in the mean time, you might be able to use NcML to solve your problem.
Here's an example that works with the IDV (open it using I'm Feeling Lucky
or with the Grib files Data Source Type):

<netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";>
   <variable name="time" shape="time" type="int">
     <attribute name="units" value="hour since 2006-09-13T00:00:00Z"/>
     <attribute name="_CoordinateAxisType" value="Time" />
     <values start="0" increment="6" />
   </variable>
<aggregation type="joinExisting" dimName="time">
<netcdf location="fnl_060913_00_00"/>
<netcdf location="fnl_060913_06_00"/>
<netcdf location="fnl_060913_12_00"/>
</aggregation>
</netcdf>

basically, you define the time variable and it's values, then use
the aggregation tag to list the files you want to aggregate. 

Save this in a text file with the extension .ncml (eg. ryan.ncml)
and place it in the same directory as the files.   Alternatively,
you can specify the full path name to the file like:

<netcdf location="file:/C:/data/grids/fnl_060913_00_00">
 
> Thanks much for any suggestions.

Let me know if that doesn't work for you.  I tested this with
version 2.5b1 (nightly build).

Don

> -----
> 
> Hi Tim-
> 
> Tim Axelrod wrote:
> > I'd like to be able to use a set of NARR-A grb files as a data source to
> > IDV and be able to display them as an animation and/or use the data
> > probe/time series tool. I'm able to do this with NAM grb files by
> > selecting "aggregated GRIB files" as the data source type. This fails
> > with the NARR-A grb files, however. Only a single time gets shown in the
> > field selector/times window - and that time seems to be randomly selected
> > from the set of files.
> 
> This is not possible at present but a solution is being worked on
> in the underlying netCDF-Java layer. But that won't be available
> for a few months.
> 
> The NAM works because they all have the same model run time and each
> file has an offset forecast hour. Each NARR file has a different
> base ("model run") time with a forecast hour of 0, so the aggregation
> doesn't know what to use as a "model run" time.
> 
> > I'm using IDV 2.3, build data 2007-08-15. Any advice?
> 
> If you are daring, you could run the nightly build which has
> formula in it for making a time sequence from a set of single time
> images or grids. What you would do is select all the NARR files you
> want to "aggregate" and use the I'm Feeling lucky option in the
> Files Chooser. Then use the "Miscellaneous->Make a time sequence from
> single time grids/images" formula. That will pop up a dialog that
> allows you to select the individual grids. This will be time consuming
> if you have a lot of files. It's a a new feature (multiple parameter
> selection), so feedback is welcome.
> 
> The nightly build is available at:
> 
> http://www.unidata.ucar.edu/software/idv/release/nightly
> 
> Don Murray
> *************************************************************
> Don Murray UCAR Unidata Program
> dmurray@hidden_host P.O. Box 3000
> (303) 497-8628 Boulder, CO 80307
> http://www.unidata.ucar.edu/staff/donm
> *************************************************************
> 
> 


Ticket Details
===================
Ticket ID: CLG-761846
Department: Support IDV
Priority: Normal
Status: Open