[MITgcm-support] Artificial Zonal Symmetries

[Alon Stern]

Hello

My name is Alon Stern, and I am a Phd student at the Courant Institute
at NYU. I have been using MITGCM for the last few months to try
simulate the Antarctic Circumpolar Current.

I have set up the model to be a channel: Solid (no slip) boundaries in
the north and south, and periodic boundaries on the east and west of
the domain. I am forcing the fluid with a wind stress which is
constant in the x-direction.

I am using the following setup in my SIZE.h file

sNx=35
sNy=50
OLx=4
OLy=2
nSx=2
nSy=2
nPx=6
nPy=6
Nx=sNx*nSx*nPY
Ny=sNy*nSy*nPy
Nr=25


The problem that I am facing is that the results of the simulation
come out to be zonally periodic in the x-direction, with 6 copies of
the same pattern in the domain. Ie: I see the same eddy pattern repeat
6 times in the zonal direction. It seems that this is occurring
because nPx=6. I have done tests with other amounts of processors and
I get the same issue with the same pattern repeating a number of times
equal to the number of processors in the x-direction.

I have tried to change the number of processors in the middle of a
simulation, and in this way I can lower the number of symmetries down
to 2, but I can not get rid of them completely.

Do you have any idea what is causing this effect, and how I can get
rid of it? Please let me know if I have not been sufficiently clear
with describing the problem.

Thanks
Alon
alon at cims.nyu.edu