[MITgcm-support] Effect of 'vectorInvariantMomentum' flag on first order circulation

[Dhruv Balwada]

Hi MITgcm community,

I have recently been stumped an issue with the MITgcm vectorInvariantMomentum
flag.

**The model setup** is meant to be an ideal representation of the ACC
(following Abernathey and Cessi 2014). It has the following components -
a) Linear temperature relaxation at the surface
b) Zonal wind with sinusoidal structure
c) Initial temp field is zonally symmetric and the thermocline shoals from
north to south (similar to the ACC).
d) Resolution is 20km, and domain size is 2000km * 2000km.
e) Zonally periodic and meridional walls
f) A zonal gaussian bump is the topographic feature, which is meridionaly
independent.

**The issue** I am facing is that the circulation pattern completely
changes when I change the "vectorInvariantMomentum" flag.
When the flag is set to false (default), the model recreates an ACC like
flow. Flow is from west to east and strongly perturbed by the presence of
topography.
When the flag is set to true (default), the model does something else. Flow
is from east to west, with a strong boundary flow from the west to east
near the southern boundary.

Any help would be appreciated.

I have posted some visualizations and data file here -
https://sites.google.com/site/dhruvbalwada/blog/mitgcmissuewithvectorinvariantmomentumflag

Here is the data file (obviously the vectorinvariantmomentum flag is
changed between two runs.

 &PARM01

# viscosity

 viscAr=5.6614E-04,

 viscC4Leith=2.15,

 viscC4Leithd=2.15,

 viscA4GridMax=0.8,

 useAreaViscLength=.TRUE.,

 highOrderVorticity=.TRUE.,

# diffusivity

 tempAdvScheme=7,

 diffKrT=5.44e-7,

 saltStepping=.FALSE.,

 staggerTimeStep=.TRUE.,

# multiDimAdvection=.TRUE.,

 vectorInvariantMomentum=.TRUE.,

# initial vertical profiles of T and S

 sRef=30*35.0000,

# equation of state

 eosType='LINEAR',

 tAlpha=2.0E-04,

 sBeta=0.0,

# boundary conditions

 no_slip_sides=.FALSE.,

 no_slip_bottom=.TRUE.,

# bottomDragLinear=1.1E-03,

 bottomDragQuadratic=0.0021,

# physical parameters

 f0=-0.9E-04,

 beta=1.0E-11,

 gravity=9.81,

# implicit diffusion and convective adjustment

 implicitDiffusion=.TRUE.,

 implicitViscosity=.TRUE.,

# exact volume conservation

 exactConserv=.TRUE.,

# C-V scheme for Coriolis term

 useCDscheme=.FALSE.,

# partial cells for smooth topography

 hFacMin=5.0E-02,

# file IO stuff

 readBinaryPrec=64,

 useSingleCpuIO=.TRUE.,

 debugLevel=1,

 &
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