Using gradsnc to read the CCSM3 POP (ocean) data

[Jamie Scott]

Yes, I used pop_remap.ncl to interpolate.   It sound like you haven't
defined / named
your coordinate dimensions properly.   Can you send the output from
"ncdump -h yourfile.nc"
to verify?


On Feb 9, 2006, at 9:50 AM, Ching-Yee wrote:

> Thank you all for your reply.
>
> I know that POP data are in different grid and needed to be
> interpolated,
> which I've done by using ncl pop_remap.ncl script (suggested by the
> CCSM3
> user guide). It seems that the output data from the pop_remap.ncl
> have the
> same grid that's readable by gradsnc (for example the output from
> CAM3),
> however, I still got the same response from gradsnc when using
> sdfopen.
> Maybe I still don't understand ncl and /or netCDF files enough.( It
> might
> not be appropriate to ask details about my ncl script.)
>
> James, do you use pop_remap.ncl to do the interpolation?
>
> Eric, I'd like to know how to use matlab to read the data. Can you
> please
> send me your matlab script?
>
> Thank you all very much.
>
> Ching-Yee
>
>
> -----Original Message-----
> From: Eric DeWeaver [mailto:deweaver at aos.wisc.edu]
> Sent: Thursday, February 09, 2006 11:15 AM
> To: Ching-Yee
> Cc: GRADSUSR at LIST.CINECA.IT
> Subject: Re: Using gradsnc to read the CCSM3 POP (ocean) data
>
>
> Hi Ching-Yee,
>
> I think the trouble is that the ocean model uses a grid in which
> the pole
> is displaced to Greenland.  I had the same problem with the CCSM3
> sea ice
> data.  With the sea ice data, output from ncdump -h includes
>
>         float TLON(nlat, nlon) ;
>                 TLON:long_name = "T grid center longitude" ;
>                 TLON:units = "degrees_east" ;
>         float TLAT(nlat, nlon) ;
>                 TLAT:long_name = "T grid center latitude" ;
>                 TLAT:units = "degrees_north" ;
>         float ULON(nlat, nlon) ;
>                 ULON:long_name = "U grid center longitude" ;
>                 ULON:units = "degrees_east" ;
>         float ULAT(nlat, nlon) ;
>                 ULAT:long_name = "U grid center latitude" ;
>                 ULAT:units = "degrees_north" ;
>                 ULAT:comment = "Latitude of NE corner of T grid
> cell" ;
>
> So instead of having a "discernable x-coordinate" there are arrays
> which
> give the latitude and longitude of the (i,j)th grid cell.  To make
> things
> even more complicated, it's a B-grid, so there are different latitudes
> and longitudes for the temperature and the velocity.
>
> I couldn't find a way to plot this in grads.  I did it in matlab, and
> I'll be happy to send you the script.  One other suggestion: PCMDI has
> ocean and sea ice data for the IPCC AR4 model simulations which has
> been
> regridded to a standard lat/lon grid.  I know they have some data from
> CCSM3, maybe they have the stuff you want.  Their webpage is
>
>   http://www-pcmdi.llnl.gov/ipcc/about_ipcc.php
>
> Also, they might have a code that converts from the ocean model grid
> to a lat/lon grid.  Either that or somebody at NCAR has a code that
> does it (maybe an ncl code?).  You could contact the NCAR ocean
> model working group, they have a community liason who might know
> (see http://www.ccsm.ucar.edu/working_groups/Ocean/).
>
> Best Wishes,
>
> Eric
>
>
> On Thu, 9 Feb 2006, Ching-Yee wrote:
>
>> Dear grads users,
>> I would like to use gradsnc to read the CCSM3 ocean model (POP)
>> output
> data
>> (in netCDF format), but when I use sdfopen the data, it said that
>> "SDF
> file
>> has no discernable X coordinate."
>> I know there are CCSM3 POP output data that are placed at PCMDI/IPCC
> website
>> which are also in netCDF format, but accessible via gradsnc
>> (sdfopen).
>>
>> Does anyone have any suggestions on how to use gradsnc to read the
>> data?
>>
>> Thank you in advance.
>>
>> Ching-Yee
>>