[MITgcm-support] advection scheme

[Christopher L. Wolfe]

Julie,

I think you could get away with reducing both your horizontal  
viscosity and your horizontal diffusivity. I'm running a model with 5  
km resolution and I have Ah = 10 and Kh = 1e-5. I also have a  
hyperviscosity of A4 = 5e8 to prevent too much energy from  
accumulating at the grid scale. Everything is quite stable with a  
time step of 500 s. The smallness of my horizontal Laplacian  
viscosity is limited by the need to resolve the Munk layers on the  
western boundary. Since you have beta = 0, you may be able to push  
the horizontal viscosity even lower.

I'm also using a nonlinear flux limiter (scheme 33) with good  
results. I'm not sure what effect it has on the eddies; I use it  
primarily to avoid the generation of spurious temperature extrema.

What kind of surface forcing are you using? That can have a great  
impact on how many eddies form.

Christopher

-----------------------------------------------------------
Dr. Christopher L. Wolfe                   858-534-4560
Physical Oceanography Research Division    OAR 357
Scripps Institution of Oceanography, UCSD  clwolfe at ucsd.edu
-----------------------------------------------------------



On Aug 27, 2007, at 12:48 PM, Julie Deshayes wrote:

> hello,
> I am running a configuration of the model at high latitude (f=1e-4 / 
> s). my domain is 700km x 700km and the resolution is 10 km. I do  
> not have as many eddies as I expected, so I am running some tests  
> to decrease the values of viscAh and diffKhT that I am using now  
> (see data file at the end of my email). I hope that this will give  
> me more eddies. Besides, I am thinking of changing the advection  
> scheme (currently centered 4th order) to a non-linear flux limited  
> scheme. Would you recommend me to do that ? or, considering my  
> configuration, what advection scheme would you recommend me to use ?
> thank you in advance for your help,
> Julie
>
>
>
>
> # Model parameters
> #
> # Continuous equation parameters
>  &PARM01
>  readBinaryPrec=64,
>  useSingleCpuIO=.TRUE.,
>  tRef=  5.35, 5.20, 5.05, 4.9, 4.75, 4.6, 4.45, 4.3, 4.15, 4.0,
>  sRef=10*10.,
>  rigidLid=.FALSE.,
>  implicitFreeSurface=.TRUE.,
>  hFacMin=0.2,
>  no_slip_sides=.TRUE.,
>  no_slip_bottom=.TRUE.,
>  bottomDragLinear=1.e-6,
>  eosType='LINEAR',
>  tAlpha=2.E-4,
>  sBeta =0.,
>  saltStepping=.FALSE.,
>  tempAdvScheme=4,
>  saltAdvScheme=4,
>  diffKhT=120.,
>  diffKzT=1.E-5,
>  f0=1.0e-4,
>  beta=0.E-11,
> # useCDscheme=.FALSE.,
>  useNHMTerms=.FALSE.,
>  implicitDiffusion=.TRUE.,
>  ivdc_kappa=1000.0,
>  viscAz=2.E-4,
>  viscAh=200.,
>  &
> #
> # Elliptic solver parameters
>  &PARM02
>  cg2dMaxIters=1000,
>  cg2dTargetResidual=1.E-11,
>  &
> #
> # Time stepping parameters
>  &PARM03
> startTime=622080000.,
>  endTime=933120000.,
>  deltaT=1500.0,
>  abEps=0.1,
>  pChkptFreq=0.0,
>  chkptFreq=311040000.,
>  dumpFreq=311040000.,
> # taveFreq=86400.,
>  cAdjFreq=0,
>  &
>
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support