[MITgcm-support] problem of open boundary

[Martin Losch]

Hi Tongya,

please have a look at your salinity and temperature fields near the boundary. This looks very much like  a flow introduced because there is a strong density gradient accross the boundary. Maybe your HYCOM temperature/salinity are in conflict the the local surface forcing?

Turning on the sponge layer may aleviate the problem, but maybe it will only move it further inward.

Martin

> On 31 Mar 2015, at 04:43, Tongya Liu <liutongya13 at mails.ucas.ac.cn> wrote:
> 
> Hi all,
> 
> I met a very strange prolem in my model recently. My model terrain is 109-135E&0-30N(the grid is 360*300). The northern,eastern and southern boundary are open boundaries. HYCOM flow feild is used to supply the open boundary velocity. But there is a strong northward flow just close to the eastern boundary, whose velocity and direction is quite different from the eastern boundary. It seems that the boundary input didn't work in this place.  This strange flow has influenced the interior circulation. I adjusted the boundary velocity and the boundary conditions, but it still exist. 
> 
> I show the result in this web: http://photo.blog.sina.com.cn/photo/1955901475/0028mLjZgy6R7I55jUIf0#pic
> 
> Please give me some advices. Thanks very much.
> 
> Tongya Liu
> 
> data:
> 
> # ====================
> # | Model parameters |
> # ====================
> #
> # Continuous equation parameters
>  &PARM01
> 
>  viscAr=1.77E-3,
>  viscAh=100,
>  diffKhT=0,
>  diffKrT=3E-5,
>  diffKhS=0,
>  diffKrS=3E-5,
>  useFullLeith=.TRUE.,
>  viscC4Leith=1.5,
>  viscC4Leithd=1.5,
>  viscA4GridMax=1.0,
>  useAreaViscLength=.TRUE.,
>  useAnisotropicViscAGridMax=.TRUE.,
>  tempAdvScheme=33,
>  saltAdvScheme=33,
>  eosType = 'JMD95Z',
>  multiDimAdvection=.TRUE.,
>  vectorInvariantMomentum=.TRUE.,
> 
>  no_slip_sides=.FALSE.,
>  no_slip_bottom=.TRUE.,
>  bottomDragQuadratic=0.0025,
>  implicitDiffusion=.TRUE.,
>  implicitFreeSurface=.TRUE.,
>  implicitViscosity=.TRUE.,
>  staggerTimeStep=.TRUE.,
>  implicitFreeSurface=.TRUE.,
> &n bsp;exactConserv=.TRUE.,
>  hFacMin=0.3,
>  hFacMindr=50.,
>  hFacInf=0.1,
>  hFacSup=5.,
>  readBinaryPrec=64,
> #- not safe to use globalFiles in multi-processors runs
>  globalFiles=.TRUE.,
>  useSingleCpuIO=.TRUE.,
>  &
> 
> # Elliptic solver parameters
>  &PARM02
>  cg2dMaxIters=500,
>  cg2dTargetResidual=1.E-5,
>  &
> 
> # Time stepping parameters
>  &PARM03
>  nIter0=        0,
>  nTimeSteps = 25920,
> #nTimeSteps = 200,
> #startTime=0.,
> #endTime=311040000.,
>  basetime=0,
>  deltaT=1200.0,
>  abEps=0.1,
>  momDissip_In_AB=.FALSE.,
>  dumpFreq=864000,
>  pChkptFreq=31104000.,
>  chkptFreq=2592000.,
>  monitorSelect=2,
>  monitorFreq=864000.,
> 
>  &
> 
> # Gridding parameters
>  &PARM04
>  usingSphericalPolarGrid=.TRUE.,
>  ygOrigin=0.0,
>  xgOrigin=99.,
>  dxSpacing=0.1,
>  dySpacing=0.1, 
>  delR=30.,30.,30.,30.,30.,30.,
>        30.,30.,30.,30.,30.,30.,
>        30.,30.,30.,30.,30.,30.,
>        30.,30.,50.,50.,100.,200.,
>        300.,500.,600.,800.,800.,1000.,
>  &
> 
> # Input datasets
>  &PARM05
>  bathyFile='topog.bin',
>  hydrogThetaFile='Temp.bin',
>  hydrogSaltFile='Salt.bin',
> 
>  &
> 
> data.obcs
> 
> # Open-boundaries
>  &OBCS_PARM01
> # open boundaries.
>  OBCSfixTopo=.FALSE.,
>  OB_Jnorth= 360*-1,
>  OB_Jsouth= 360*1,
>  OB_Ieast = 300*-1,
> 
>  useOBCSprescribe = .TRUE.,
> #useOBCSsponge=.TRUE.,
>  
>  useOBCSbalance=.TRUE.,
>  OBCS_balanceFacN= 1.,
>  OBCS_balanceFacS= 1,
>  OBCS_balanceFacE= 1.,
> 
>  OBNuFile = 'HY_No rthU.bin',
>  OBSuFile = 'HY_SouthU.bin',
>  OBEuFile = 'HY_EastU.bin',
>  OBNvFile = 'HY_NorthV.bin',
>  OBSvFile = 'HY_SouthV.bin',
>  OBEvFile = 'HY_EastV.bin',
> 
>  OBNsFile = 'snorth.bin',
>  OBNtFile = 'tnorth.bin',
>  OBEsFile = 'seast.bin',
>  OBEtFile = 'teast.bin',
>  OBSsFile = 'ssouth.bin',
>  OBStFile = 'tsouth.bin',
> 
>  OBCS_monitorFreq= 2592000.,
>  OBCS_monSelect = 1,
>  &
> 
> # *****************************************
> # Sponge Layer Parameters.
> # *****************************************
>  &OBCS_PARM03
>  Urelaxobcsinner=432000.E0,
>  Urelaxobcsbound=43200.E0,
>  Vrelaxobcsinner=432000.E0,
>  Vrelaxobcsbound=43200.E0,
>  spongeThickness=30,
>  &
> 
> 
> 
> 
> 
> 
> 
> 
> 
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