[Go-essp-tech] CMOR and cell_measures issues

[Bentley, Philip]

Hi Balaji,
 
> Phil, I'm very impressed that Had will have gridspec files, 
> is this a done deal? I've been so pessimistic about this that 
> I was wondering if even we should do one ourselves.

Nope, not a done deal yet :-(

In line with the CMIP5 expt design doc, we don't really need to provide
gridspec files since all our model output is on either regular or
uniform grids (i.e. simple cartesian product of lat & long).

However, this whole cell_measures business prompted me to revisit the
gridspec tools and output, which reminded me that the gridspec netcdf
files include a cell area variable. Which in turn means we wouldn't need
to provide a separate file (or files) for cell areas. Hence we could
drop the ext_cell_measures attribute from our CMIP5 output files.

Using the gridspec tools may be a quick and easy way for us to provide
cell area info if we need to.

Caveat: from a quick glance it looks like the netcdf files produced by
the gridspec tools are not CF compliant. Is this is an issue? Presumably
it is if we want all the data in the CMIP5 archive to be CF compliant.
(NB: it could be I'm not running with the very latest version of the
tools - but I couldn't see a more recent version on the gfdl web site).

> You know of course that gridspec says you can supply
> 
> > gridspec_fx_HadGEM2-ES_atm_pgrid.nc
> > gridspec_fx_HadGEM2-ES_atm_ugrid.nc
> > gridspec_fx_HadGEM2-ES_atm_vgrid.nc
> > gridspec_fx_HadGEM2-ES_atm_uvgrid.nc
> 
> as one single supergrid...

If I could figure out how to output all 7 or 8 atm/ocn (sub-)grids to a
single netcdf file I would, but the available documentation (e.g. for
make_hgrid) isn't clear on this point. Sorry, that's probably just me
being dumb! But if there is updated documentation then please point me
to it. If necessary I could concatenate variables afterwards using NCO
tools.

Right now I'm trying to figure out how to create a gridspec file for our
HadGEM2 ocean model, which uses a stretched (i.e. tartan/plaid) grid:
longitudes are evenly spaced, latitudes vary from 1 deg to 1/3 deg.
(Looks like I need to use the --my_grid_file option to supply the
lat/long coords).
> 
> But if you're doing gridspec at all, I will concede this 
> point:-). Let's both do these separate gridspecs for now.

Works for me.

I think we're suffering from 'early-adopter syndrome' :-/

Cheers,
Phil

> 
> Bentley, Philip writes:
> 
> > Hi Karl,
> >
> > A somewhat belated follow-up question in connection with 
> this proposal 
> > (and with some slight overlap with Jamie's email which 
> crossed on the 
> > ether)...
> >
> > As things stand the files named in the 'associated_files' attribute 
> > appear thus (using our RCP 4.5 simulation as an example):
> >
> > "... gridspecFile: gridspec_fx_HadGEM2-ES_rcp45_r0i0p0.nc areacella:
> > areacella_fx_HadGEM2-ES_rcp45_r0i0p0.nc"
> >
> > Are the <expt_id>_<rip> parts (i.e.  'rcp45_r0i0p0.nc' ) actually 
> > required? AFAIK, our gridspec/cellarea files will not 
> change from one 
> > simulation to the next using the same model (HadGEM2-ES in 
> this case).
> >
> > Since, like most centers, we will be running large numbers of 
> > simulations using the same model, it looks like we would need to 
> > create numerous duplicates of the gridspec/cellarea files - 
> or lots of 
> > symlinks
> > - in order to for these references to make sense. Unless you are 
> > planning to manage that on our behalf somehow...?
> >
> > I think our 4 gridspec files for the HadGEM2 atm grids are 
> likely to 
> > be called something like...
> >
> > gridspec_fx_HadGEM2-ES_atm_pgrid.nc
> > gridspec_fx_HadGEM2-ES_atm_ugrid.nc
> > gridspec_fx_HadGEM2-ES_atm_vgrid.nc
> > gridspec_fx_HadGEM2-ES_atm_uvgrid.nc
> >
> > So without any simulation-specific info. (There would also be files 
> > for the ocean grids)
> >
> > As it happens the gridspec files contain grid cell areas, 
> so I'm now 
> > wondering if we'd even supply both?
> >
> > I'd be interested to hear your thoughts on this. I may be 
> > mis-understanding something/everything :-)
> >
> > Regards
> > Phil