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

Ryan Abernathey ryan.abernathey at gmail.com
Wed May 7 14:43:09 EDT 2014


Thanks for all the helpful suggestions everyone!
I am now convinced that this isn't as "unphysical" as I thought.

In response to Christopher's suggestions, does anyone know whether I should
have convective adjustment active together with GGL90? I know for KPP you
are supposed to turn off all convective adjustment. Is that also the case
for GGL?

Thanks again,
Ryan


On Wed, May 7, 2014 at 2:10 PM, Christopher L. P. Wolfe <
christopher.wolfe at stonybrook.edu> wrote:

>
> My guess that you’re seeing hydrostatic convection. You don’t seem to have
> set either cAdjFreq or ivdc_kappa and my understanding is that they both
> default to zero. So, your model’s trying to do convection through the
> momentum equations and the convective scale is smaller than your grid
> spacing (hydrostatic convection runs to the grid scale).
>
> Christopher
>
>
> On May 7, 2014, at 1:20 PM, Ryan Abernathey <ryan.abernathey at gmail.com>
> wrote:
>
> 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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