Issues with regional MOM6 when using 1-degree resolution ocean forcing data

ANCOMS
1

I’ve been trying to generate forcing data using 1° monthly ACCESS-OM2 output, whereas the examples I’ve seen use 0.1° daily data. I’ve run into two issues so far:

  1. I use the monthly data to create access_om2_input, and from this the boundary forcing files (north/south/east/west_unprocessed.nc). When these files are passed to expt.setup_ocean_state_boundaries (the updated version of expt.rectangular_boundaries in the example recipes), the function assumes the input is daily data. The boundary forcing files it generates don’t cover the full time period I expected them to, (two years of monthly data is misinterpreted as just 24 days). I don’t know if the forcing data has to be daily, or if monthly would be fine as long as it was dated correctly in the files generated!

I could get around this by adding this code in before the north/south/east/west_unprocessed.nc files are saved.

daily_time = pd.date_range(start=date_range[0], end= date_range[1], freq='D')
def interp_to_daily(ds):
    return ds.interp(time=daily_time)

## Cut out East & West boundary conditions and save to netCDF
print('East & West boundary condition...')
east = rmom6.longitude_slicer(access_om2_input,
                               [longitude_extent[1] - buffer, longitude_extent[1] + buffer],
                               ["xu_ocean", "xt_ocean"])
interp_to_daily(east).to_netcdf(tmp_dir + "/east_unprocessed.nc")
  1. The ACCESS-OM2 data I used has 50 vertical levels (nz=50), but in rmom6.experiment I had set number_vertical_layers = 75. Expt.setup_initial_condition() handled the vertical regridding correctly, and the resulting initial condition files had nz=75 as expected. Expt.setup_ocean_state_boundaries produced boundary forcing files that still only had nz=50.
    Again I could get around this by adding something like this into the notebook before calling Expt.setup_ocean_state_boundaries
rg_output_dir = tmp_dir+"/regrid/"
os.makedirs(rg_output_dir, exist_ok=True)

zl_interp = expt.vgrid.zl.rename({'zl': 'st_ocean'})
directions = ["north", "south", "east", "west"]
for direction in directions:
    input_file = os.path.join(tmp_dir, f"{direction}_unprocessed.nc")
    output_file = os.path.join(rg_output_dir, f"{direction}_unprocessed.nc")
    print(f"Interpolating {input_file}")
    ds = xr.open_dataset(input_file)
    ds_interp = ds.interp({'st_ocean': zl_interp})
    ds_interp.to_netcdf(output_file)
    print(f"Saved to {output_file}")

and using rg_output_dir as the inputput for exp.setup_ocean_state_boundaries(raw_boundaries_path=Path(rg_output_dir))

2

Thanks for posting @Lizzie. Are you hoping to get help from ACCESS-NRI with this? Adding the help tag to your post will mean it gets triaged by our support team.

See Support FAQ (Frequently Asked Questions)

3

Hey Lizzie,

I can’t really help except to say that I noticed the same thing about the boundary files still having the native vertical resolution of the forcing dataset. I think the interpolation might be handled by MOM6 although I’m not totally sure.

For your first question - if you don’t have any luck here you could try an issue on the regional-mom6 repo. I’m interested in the answer since I have just discovered that very few of the ACCESS-OM2 models save daily u, v, temp, salt, and ssh. I don’t know if i just suck at using intake, but as far as I can tell only 01deg_jra55v13_ryf9091 and 01deg_jra55v150_iaf_cycle1 have all the variables that regional-mom6 wants - and maybe they only have daily SSH in January?

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