[MITgcm-support] ISOMIP compressibility

[Arran Whiteford]

Hullo,

I'm trying to figure out what versions of the Boussinesq equations the ISOMIP tutorial example is solving
https://github.com/MITgcm/MITgcm/tree/master/verification/isomip

It includes non hydrostatic code.
#define ALLOW_NONHYDROSTATIC https://github.com/MITgcm/MITgcm/blob/master/verification/isomip/code/CPP_OPTIONS.h

In the MITgcm documents it explains:
1.3.4.4.2. Ocean
Non-hydrostatic forms of the incompressible Boussinesq equations in z- coordinates are supported - see eqs. (1.98) to (1.103).

BUT eqns (1.98) to (1.103) are not the incompressible eqns, they are the semi-compressible.
https://mitgcm.readthedocs.io/en/latest/overview/hydrostatic.html

In the non-hydrostatic ocean model all terms in equations Eqs.(1.29 →
1.31) are retained.

Which is true? Is the nonhydrostatic code running incompressible or semi-compressible Boussinesq equations?

Thanks,
Arran

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