Add netcdf file for mrsofc

[Whyborn]

This PR adds the NetCDF file for the mrsofc (soil_moisture_content_at_field_capacity) variable. This is taken from an atmosphere restart file, in combination with the CABLE soil layer thicknesses, which are not included anywhere in the ESM1.6 input or output information as far as I'm aware. The contents of the file are:

[lw5085@gadi-login-04 ~]$ ncdump -h mrsofc_fx_ACCESS-ESM1-6.nc 
netcdf mrsofc_fx_ACCESS-ESM1-6 {
dimensions:
	lon = 192 ;
	lat = 145 ;
variables:
	double lon(lon) ;
		lon:_FillValue = NaN ;
		lon:units = "degrees_east" ;
	double lat(lat) ;
		lat:_FillValue = NaN ;
		lat:units = "degrees_north" ;
	double mrsofc(lat, lon) ;
		mrsofc:_FillValue = NaN ;
		mrsofc:standard_name = "soil_moisture_content_at_field_capacity" ;
		mrsofc:long_name = "Capacity of Soil to Store Water (Field Capacity)" ;
		mrsofc:units = "kg m-2" ;
		mrsofc:cell_methods = "area: mean where land" ;
		mrsofc:modelling_realm = "land" ;
		mrsofc:processing_notes = "Excludes lake water and refers to soil water only." ;
}

I can easily add any additional metadata if necessary, and a description somewhere.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.5%. Comparing base (cde9572) to head (8ac327e).

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[rhaegar325]

The mrsofc variable is not yet included in the current ACCESS-ESM1.6_mappings. It will be tested after the relevant variable information is added to the mappings.

related pr #220

[Whyborn]

@rhaegar325 do you require any action from me at this point?

[rhaegar325]

The mrsofc variable is not yet included in the current ACCESS-ESM1.6_mappings. It will be tested after the relevant variable information is added to the mappings.

related pr #220

Not for now, we’d like to first improve the functionality for directly reading data from NetCDF files. We’ll come back to test this PR once that is in place. Thanks again for your help @Whyborn !