[IDV #ALX-750694]: reading gridded netcdf time-series output in idv

Oops, forgot to attach the NcML file...still on my first cup of coffee!

Sean

> Greetings Larry!
> 
> I've taken a look at your file, and you are correct that the issue is that it 
> is not
> CF compliant. I've attached an NcML file to this email, and if you place this 
> in
> the same directory as your netCDF file and load it (the NcML file) into the 
> IDV,
> things will work as you expect.
> 
> This fix will allow you to use the IDV with your model out. Please keep in 
> mind
> that this will not make it CF compliant, but rather "good enough" for the IDV.
> 
> The main issue:
> 
> The time variable, t, has a unit attribute set to hours and a attribute 
> ReferenceTime
> set to the reference time - in order to be CF compliant, the reference time 
> must
> be part of the unit:
> 
> attribute unit : "hours since 1991-03-19 18:00:00"
> (see 
> http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#time-coordinate)
> 
> All this NcML file does is change the attribute unit on the time variable t. 
> Note that
> if you want to use this on a different file, you will need to edit the second 
> line of the
> NcML file to correctly reference the new netCDF file. To make life easier, 
> you may
> want to contact the modeling group and see if they would fix the unit for t 
> in their
> code.
> 
> Also, I would strongly recommend that when working with this data, you use the
> "Predefined -> South America" projection and turn off the option "Auto-set
> Projection" - both are found under the Projections menu just above the main
> view window. If you don't do this, you will get some pretty funky artifacts 
> due
> to the prime meridian.
> 
> Cheers!
> 
> Sean
> 
> > Dear support-idv:
> >
> > I am unable to import a time-varying 2-d gridded netcdf variable into idv
> > and was wondering if you might have some advice as to what I'm doing wrong.
> >
> > For example, I am using the following netcdf file:
> > ftp://ftpext.usgs.gov/pub/wr/wa/vancouver/Mastin/Ash3d/3d_tephra_fall.nc
> >
> > I am attempting to read the 2-D, time-dependent variable cloud_load, whose
> > properties are given as follows when I type "ncdump -h"
> >
> > double cloud_load(t, lat, lon) ;
> > cloud_load:long_name = "Cloud Load" ;
> > cloud_load:units = "T/km2" ;
> > cloud_load:missing_value = "-9999.f" ;
> > cloud_load:_FillValue = -9999. ;
> >
> > When I open this file using the IDV data chooser, only three variables are
> > visible, as you can see in the attached screenshot:
> >
> > Deposit arrival time
> > Airborne ash arrival time
> > Cell area
> >
> > These variables are 2-D gridded, non-time dependent variables, having the
> > dimensions:
> >
> > double depotime(lat, lon) ;
> > double ash_arrival_time(lat, lon) ;
> > double area(lat, lon) ;
> >
> > The netcdf file contains several other variables with dimensions (t, lat,
> > lon), like cloud_load, but none of these show up.
> >
> > Our modeling group wrote the code that creates the netcdf file and we think
> > the file is nf-compliant.
> >
> > Do you think this is an issue involving compliance with netcdf conventions,
> > or is there a trick to viewing time-dependent gridded netcdf data that I
> > haven't yet found?
> >
> > Your help would be appreciated.
> >
> > Thanks,
> >
> > Larry Mastin
> >
> >
> > --
> > U.S. Geological Survey
> > David A. Johnston Cascades Volcano Observatory
> > 1300 SE Cardinal Court, Bldg. 10, Suite 100
> > Vancouver, WA 98683 USA
> > tel. (360) 993-8925
> > fax (360) 993-8980
> >
> >


Ticket Details
===================
Ticket ID: ALX-750694
Department: Support IDV
Priority: Normal
Status: Open

Attachment: 3d_tephra_fall.ncml
Description: Binary data