Using gradsnc to read the CCSM3 POP (ocean) data

[Ching-Yee]

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