[MITgcm-support] Help me get rid of my noise!

[Ryan Abernathey]

I guess my image didn't make it through on that last email.



On Wed, May 7, 2014 at 1:11 PM, Ryan Abernathey
<ryan.abernathey at gmail.com>wrote:

> Hello MITgcm Support Group,
>
> I am running a 2D model (depth and latitude) in a Southern Ocean
> configuration. I am trying to eliminate what appears to be unphysical
> grid-scale noise in my W field--columns of alternately very high and low W.
> This is a snapshot of W after 5 years of spinup. This pattern is steady in
> time.
>  As you can see, the noise is concentrated mainly (but not exclusively)
> over the shelf break. A possibly related issue is that my cg2d solver is
> relatively far from convergence:
> cg2d: Sum(rhs),rhsMax =  -5.46186194609888E-05  6.64557830841732E-02
>
> My model is 0.5 degree resolution in latitude, meaning that it is
> relatively high resolution compared to the tutorials (e.g. ideal_2D_oce),
> but of course it has no eddies or any temporal variability at all, since it
> is 2D. This puts it in an unknown [at least to me] parameter regime.
>
> I have tried cranking the lateral viscosity (both laplacian and
> biharmonic) up as high as they will go. I have enabled both linear and
> quadratic bottom drag. I am NOT using the CD scheme; the noise was much
> worse with it enabled. I am NOT using KPP but rather GGL90. (I tried with
> KPP and it was not very different.)
>
> I would appreciate any suggestions you have about how to get rid of this
> noise and achieve smooth fields.
>
> Thanks,
> Ryan
>
> ####### data file ##########
>  &PARM01
>  useAreaViscLength=.FALSE.,
>  viscAr=1.0E-03,
>  viscA4=1e12,
>  viscAh=1e5,
>  tempAdvScheme=77,
> # KrT fields are read in from a file
>  diffKrT=0.0E-5,
>  diffKhT=0.0,
>  diffK4T=0.0,
>  staggerTimeStep=.TRUE.,
> # initial vertical profiles of T and S
>  tRef=44*0.0,
>  sRef=44*35.0,
> # equation of state
>  eosType='LINEAR',
>  rhonil=1035.,
>  eosType='LINEAR',
>  tAlpha=2.000000E-04,
>  sBeta=0.000000E+00,
>  saltStepping=.FALSE.,
> # boundary conditions
>  no_slip_sides=.FALSE.,
>  no_slip_bottom=.TRUE.,
> # needed for points above the U sponge layer (shelf)
>  bottomDragLinear=1.E-3,
>  bottomDragQuadratic = 0.0012
> # additional drag is done with RBCS
> # physical parameters
>  gravity=9.810000E+00,
> # implicit diffusion and convective adjustment
>  implicitDiffusion=.TRUE.,
>  implicitViscosity=.TRUE.,
>  implicitFreeSurface=.TRUE.,
> # exact volume conservation
> # exactConserv=.TRUE.,
> # C-V scheme for Coriolis term
>  useCDscheme=.FALSE.,
> # partial cells for smooth topography
>  hFacMin=5.000000E-02,
> # file IO stuff
>  readBinaryPrec=64,
>  useSingleCpuIO=.TRUE.,
>  debugLevel=1,
>  &
> # elliptic solver parameters
>  &PARM02
>  cg2dMaxIters=500,
>  cg2dTargetResidual=1E-09,
>  &
> # timestepping parameters
>  &PARM03
>  nIter0=0000172800,
> # nTimeSteps=1000,
> # nTimeSteps=12961,
>  nTimeSteps=345600,
> # deltaT=3600.0,
> # deltaT=2400.,
> # deltaT=1800.0,
>  deltaT=900.0,
>  abEps=0.1,
> # needed for sea ice
>  forcing_In_AB = .FALSE.,
>  ChkptFreq=31104000.
>  pChkptFreq=311040000.,
>  taveFreq=311040000.0,
>  dumpFreq=31104000.,
>  monitorFreq=2592000.0,
>  tauThetaClimRelax=2592000.0,
>  dumpInitAndLast=.TRUE.,
>  pickupStrictlyMatch=.FALSE.,
>  &
> # gridding parameters
>  &PARM04
>  usingSphericalPolarGrid=.TRUE.,
>  delX=0.5,
>  delY=100*0.5,
>  xgOrigin=0.,
>  ygOrigin=-80.,
>  delR=10., 10., 10., 10., 10., 10., 10., 12., 14.,
>   16.,   19.,   22.,   26.,   30.,   36.,   42.,   50.,   60.,
>   72.,   85.,  100.,  120.,  140.,  166.,  200.,  200.,  200.,
>   200.,  200.,  200.,  200.,  200.,  200.,  200.,  200.,  200.,
>   200.,  200.,  200.,  200.,  200.,  200.,  200.,  200.
>  &
> # Input datasets
>  &PARM05
>  bathyFile='bathyFile_shelf_2Dchan.bin',
>  zonalWindFile='zonalWindFile.bin',
>  thetaClimFile='thetaClimFile_WOA98_2Dchan.bin',
>  diffKrFile='diffKrFile_nosponge_2Dchan.bin',
>  hydrogThetaFile='hydrogThetaFile_WOA98_2Dchan.bin',
>  hydrogSaltFile='hydrogSaltFile_WOA98_2Dchan.bin',
>  &
>
> ########## data.pkg ##############
>  &PACKAGES
>   useMNC         = .TRUE.,
>   useGMREDI      = .TRUE.,
>   useGGL90       = .TRUE.,
>   useRBCS        = .TRUE.,
>  &
>
> ######## data.gmredi ##############
>  &GM_PARM01
>   GM_MNC             = .FALSE,
>   GM_AdvForm         = .TRUE.,
>   GM_UseBVP          = .TRUE.,
>   GM_background_K    = 2000,
>   GM_isopycK         = 2000,
>   GM_Kmin_horiz      = 50,
>   GM_taper_scheme    = 'dm95',
>   GM_BVP_ModeNumber  = 1,
>   GM_BVP_cMin        = .1,
>  &end
>
> ########### data.ggl90 ############
>  &GGL90_PARM01
>  GGL90writeState=.FALSE.,
>  GGL90TKEmin = 1.e-7,
>  mxlMaxFlag=2,
>  GGL90mixingLengthMin=3.,
>  &
>
>
> ############ SIZE.h ##############
> ...
>       PARAMETER (
>      &           sNx =   1,
>      &           sNy = 100,
>      &           OLx =   4,
>      &           OLy =   4,
>      &           nSx =   1,
>      &           nSy =   1,
>      &           nPx =   1,
>      &           nPy =   1,
>      &           Nx  = sNx*nSx*nPx,
>      &           Ny  = sNy*nSy*nPy,
>      &           Nr  =  44)
> ...
>
>
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