add make_salt_sfc_restore.py

[aekiss]

Adds https://github.com/COSIMA/access-om2/blob/2911891/tools/make_salt_sfc_restore.py

This needs some tweaks to meet the requirements of the README, particularly adding provenance metadata. @ezhilsabareesh8 would you have time to do that before we merge this PR?

[aekiss]

related: COSIMA/access-om3#207

[aekiss]

From the metadata it looks like this was also needed. We should include it in the script so it's a one-step process.

ncatted -O -a units,time,m,char,months since 0001-01-01 00:00:00 salt_sfc_restore.nc
ncrename -O -v so,salt mean_salinity_of_0_and_10m.nc

ncdump -h /g/data/ik11/inputs/access-om2/input_20201102/mom_01deg/salt_sfc_restore.nc
netcdf salt_sfc_restore {
...
// global attributes:
		:comment = "This salinity distribution is based on WOA13v2 where the land values are filled in with a conjugate gradient method. It is a simple average of land-filled salinity data at the depth of 0 and 10 meters." ;
		:history = "Fri Jun 28 12:31:42 2019: ncatted -O -a units,time,m,char,months since 0001-01-01 00:00:00 salt_sfc_restore.nc\nFri Dec  1 14:47:24 2017: ncrename -O -v so,salt mean_salinity_of_0_and_10m.nc" ;
		:NCO = "netCDF Operators version 4.7.7 (Homepage = http://nco.sf.net, Code = http://github.com/nco/nco)" ;
}

[aekiss]

Oops, converting to draft. I'm not sure this is a good way to go, since this script also needs a lot of other code from https://github.com/COSIMA/access-om2/blob/master/tools. Do we want all that here as well?

[ezhilsabareesh8]

@ezhilsabareesh8 would you have time to do that before we merge this PR?

@aekiss Yes I can do that, also there are some dependencies required for make_salt_sfc_restore.py, for example make_remap_weights.py, which also needs to be included if we move make_salt_sfc_restore.py to om3-scripts.