How to make the subbasins.nc file for NEMO 4.2.2?

Versions v4.2.x
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1

Good morning

I’m setting up a new configuration with NEMO 4.2.2 and generating the domain_cfg.nc with the DOMAINcfg tool. So far so good, but I’m missing the subbasins.nc file needed to compute zonal means and MOC for the Atlantic, Pacific, Indian Oceans.
Is there a tool available to generate this file?

Thanks
/Joakim

2

Hi Joakim,

I am not aware of an plug and play tool. But you can use cdfmkmask to build the mask of one basin (CDFTOOLS/src/cdfmkmask.f90 at master · meom-group/CDFTOOLS · GitHub). Based on the usage of the tool, you can specify boundaries of your basin across the ocean (for example a strait line between Cap Leeuwin and Africa and some oblique segments in the itf) and a seed in the middle of your basin. This should return a mask for the Indian Ocean. For each boundary line, you can set a flag to include the line or not into the basin. You do it for each basin and finalise it with nco to put them all in one file. Don’t forget to do the sum of all your basin to check. You should retrieve the original NEMO mask, if not, it means you mess up your boundaries or the flag to include them in or out of each basin.

I hope it helps,

Pierre

3

Thanks Pierre!

I had a look at this tool and could not figure out how to work it. The issue was that you need to supply a text file with boundaries but I could not wrap my head around what format the file should be in.

In the end, I made my own Python script to make basin masks for eORCA1 and ORCA2 using domain_cfg.nc bathymetry. It requires a lot of care around the Caribbean and ITF but otherwise it was pretty straightforward.

I would be happy to share it in case someone else is interested.

Out of curiosity, does the NEMO community have a recommendation on what “basin” to attribute the Arctic to? I chose to include half the Arctic in the Atlantic mask, but no Arctic in the Pacific mask. But I’m not sure how to treat this actually…