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

[Jean-Michel Campin]

Hi Dhruv,

It's a strange results. Both pkgs (mom_fluxform and mom_vecinv) have been
tested and used in many different configs, and no significant recent changes
that would be suspicious. 

I suggest to try to work on a short test run:
1) long enough to detect some significant differences between the 2 cases:
  vectorInvariantMomentum=T and = F
2) short enough so that the same 2 runs could be repeated with zero compiler
 optimization (-ieee or -devel with many standard optfile).
And from there, we could work on trying to reproduce the problem on
 different machine/compiler ... etc. 
Once we are able to reproduce the problem, should not take too long to fix.

Cheers,
Jean-Michel

On Thu, Feb 23, 2017 at 02:58:53PM -0500, Dhruv Balwada wrote:
> 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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