[MITgcm-support] is Orlanski radiation condition working in the rotating rank of MITgcm?

[Martin Losch]

Hi Yi-Chih,

I can only guess what you are trying to do: You use the verification/rotating_tank setup, you probably change f0 from 0.5 to something more “polar”, e.g. 1.45e-4 for a latitude of 85.5 degN, but then your grid spacing needs to be adjusted (from the lab-scales in the original rotating_tank experiment), etc … There are many places, where you may not satify stability criteria. See here <https://mitgcm.readthedocs.io/en/latest/examples/examples.html> for examples of stability criteria in other tutorial experiments.

Introducing open boundary conditions to get rid of grid scale noise is not a good idea. Normally open boundar condition tend to be more of a problem than a solution.

Martin

> On 14. Dec 2018, at 12:57, Yi-Chih Huang <dscpln at gmail.com> wrote:
> 
> Dear MITgcm experts,
> 
>     I ran into numerical disturbances around the boundary working on the rotating rank of MITgcm in the Arctic regions.  I tried to apply Orlanski radiation condition to the rotating rank in data.obcs below.  However, the patterns with the data.obcs are almost the same as the original one.  There is no error message in the log files.  Do you think Orlanski radiation condition is working in the rotating rank of MITgcm?  How should I update the boundary conditions on MITgcm?
> 
> # Open-boundaries
>  &OBCS_PARM01
>  OB_Ieast=102*-1,
>  OB_Iwest=102*1,
>  OB_Jnorth=130*-1,
>  OB_Jsouth=130*1,
>  useOrlanskiEast=.TRUE.,
>  useOrlanskiWest=.TRUE.,
>  useOrlanskiNorth=.TRUE.,
>  useOrlanskiSouth=.TRUE.,
> # useOBCSbalance=.TRUE.,
> # OBCS_balanceFacW= 1.,
> # OBCS_balanceFacN= 0.,
>  OBCS_monitorFreq=3000.,
>  &
> 
>  &OBCS_PARM02
>  CMAX=0.5,
>  cvelTimeScale=10000.,
>  useFixedCEast=.FALSE.,
>  useFixedCWest=.FALSE.,
>  &
> 
>     Thanks much,
> 
>                Yi-Chih
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