[MITgcm-support] SOM instability after checkpoint 64e

[Spencer Jones]

Thanks very much Martin. In case anyone is interested (or has further
enlightening thoughts), the problem is in
gad_som_advect.F, where:

   noFlowAcrossSurf = rigidLid .OR. nonlinFreeSurf.GE.1
     &                            .OR. select_rStar.NE.0

yields noFlowAcrossSurf=.TRUE. even though rigidLid=.FALSE., nonlinFreeSurf=0
and select_rStar=0 in my setup. I have solved the problem for now by
setting noFlowAcrossSurf=.FALSE. in my code directory, but obviously it
would be nice if it could be fixed properly. I don't know why it's not
working as expected though.
Thanks,
Spencer





On Fri, Aug 24, 2018 at 3:59 AM, Martin Losch <Martin.Losch at awi.de> wrote:

> Hi Spencer,
>
> in doc/tag-index I found that there were changes to the advection packages
> in checkpoint64e. Maybe you can diff the files (e.g. like this: <
> https://github.com/MITgcm/MITgcm/commit/d077f4a7023faea230432dc180400e
> 4970aff0ff#diff-5cf10394edefefcf714f07bf62cf6d40> or using other git
> capabilities) and figure out which change causes the in instability in your
> setup.
>
> Martin
>
> > On 21. Aug 2018, at 21:23, Spencer Jones <spencerj at ldeo.columbia.edu>
> wrote:
> >
> > Hi everyone,
> > I'm trying to update my code tree before I start a new project, but I'm
> finding that SOM is unstable in my setup from checkpoint 64e onwards. With
> the flux limiter off (advection scheme 80), the temperature becomes large
> and negative. With the flux limiter on (advection scheme 81), the
> temperature remains positive, but I get an unphysical-looking standing wave
> in the zonal direction at mid-latitudes.
> >
> > I have tried changing the viscosity, diffusivity and various other
> things but to no avail. Does anyone know what's going on? My data file is
> pasted below.
> > Thanks very much,
> > Spencer
> >
> > # ====================
> > # | Model parameters |
> > # ====================
> > #
> > # Continuous equation parameters
> >  &PARM01
> >  tRef = 32*0.,
> >  sRef = 32*35.,
> >  no_slip_bottom=.TRUE.,
> >  no_slip_sides=.TRUE.,
> >  viscAr=1.E-4,
> >  viscAh=40.E3,
> > # diffKrT=1.E-5,
> >  diffKrNrT=0.0083, 0.0065, 0.0038,0.0014, 0.00039,0.000092,
> >            0.00003, 0.00002,0.00002,0.00002,0.00002,0.00002,
> >            0.00002,0.00002,0.00002,0.00002,0.00002,0.00002,0.00002,
> 0.00002,
> >            0.00002,0.00002,0.00002,0.00002,0.00002,0.00002,0.00002,
> 0.00002,
> >            0.00002,0.00002,0.00002,0.00002,
> > # diffKrS=2.E-5,
> >  diffKrNrS=0.0083, 0.0065, 0.0038,0.0014, 0.00039,0.000092,
> >            0.00003, 0.00002,0.00002,0.00002,0.00002,0.00002,
> >            0.00002,0.00002,0.00002,0.00002,0.00002,0.00002,0.00002,
> 0.00002,
> >            0.00002,0.00002,0.00002,0.00002,0.00002,0.00002,0.00002,
> 0.00002,
> >            0.00002,0.00002,0.00002,0.00002,
> >  rhonil=1035.,
> >  rhoConstFresh=1000.,
> >  eosType = 'LINEAR',
> >  ivdc_kappa=10.,
> >  implicitDiffusion=.TRUE.,
> >  bottomDragLinear=1.E-3,
> >  exactConserv=.TRUE.,
> >  useRealFreshWaterFlux=.FALSE.,
> >  useSingleCpuIO=.TRUE.,
> > # turn on looped cells
> >  hFacMin=.1,
> >  hFacMindr=50.,
> > # set precision of data files
> >  readBinaryPrec=32,
> >  tempAdvScheme=81,
> >  saltAdvScheme=81,
> >  staggerTimeStep=.TRUE.,
> >  debugLevel=-1,
> >  &
> >
> > # Elliptic solver parameters
> >  &PARM02
> >  cg2dMaxIters=500,
> >  cg2dTargetResidual=1.E-13,
> >  printResidualFreq=37606140,
> >  &
> >
> > # Time stepping parameters
> >  &PARM03
> >  nIter0=13000000,
> >  nTimeSteps = 4800000,
> > # 100 years of integration will yield a reasonable flow field
> > # startTime =          0.,
> > # endTime   = 3110400000.,
> >  deltaTmom = 900.,
> >  deltaTtracer= 10800.,
> >  deltaTClock = 10800.,
> >  deltaTfreesurf= 5400.,
> >  abEps = 0.1,
> >  pChkptFreq= 4320000000.,
> >  chkptFreq=  4320000000.,
> >  dumpFreq= 43200000000000.,
> >  monitorFreq=86400000.,
> > # 10 days restoring timescale for temperature
> >  tauThetaClimRelax=  864000.,
> > # 6 months restoring timescale for salinity
> > # tauSaltClimRelax = 15552000.,
> > # periodicExternalForcing=.FALSE.,
> > # externForcingPeriod=2592000.,
> > # externForcingCycle=31104000.,
> >  pickupStrictlyMatch=.FALSE.,
> >  &
> >
> > # Gridding parameters
> >  &PARM04
> >  usingSphericalPolarGrid=.TRUE.,
> >  delR= 32*125.,
> >  ygOrigin=-70.,
> >  dySpacing=0.9722,
> >  dxSpacing=0.9722,
> >  &
> >
> > # Input datasets
> >  &PARM05
> >  bathyFile=      'bathy.bin',
> >  zonalWindFile=  'taux.bin',
> >  meridWindFile=  'tauy.bin',
> >  thetaClimFile=  'sst2.bin',
> > # saltClimFile=   'lev_sss.bin',
> > # surfQFile=      'ncep_qnet.bin',
> > # the_run_name=   'global_oce_latlon',
> > # fresh water flux is turned on, comment next line to it turn off
> > # (maybe better with surface salinity restoring)
> >  EmPmRFile=      'sflux.bin',
> >  &
> >
> >
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>
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