[MITgcm-support] Numerical instability when horizontal contrast of initial temperature is large

[Christoph Voelker]

Dear Yanhong,

I have no idea what to choose as viscosity for a magma ocean, but I 
wondered about the viscosities: In the tutorial examples, which are made 
for water, one finds values like

  viscAr=1.E-3,
  viscAh=5.E5,

not so different from what you take. Should these values not be very 
much higher for Magma?

Also, how are you prescribing the equation of state?

Cheers, Christoph


On 15.11.24 08:31, 赖六娃 wrote:
> Hi,
> 
> I’m trying to simulate the magma ocean in tidally locked lava planet.
> To speed up the simulation, the initial temperature is set to decrease 
> from 3000 K at the substellar point (0,0) to 50 K at the side boundaries.
> Meanwhile, the initial temperature is vertically uniform.
> 
> However, there is strong instability when I start this simulation. I 
> tried to decrease the maximum initial temperature to 1700 K, and the 
> horizontal contrast becomes  to (1700-50) K, but it is still unstable.
> 
> Is there any way I can simulate stably with this initial temperature setup?
> By the way, the tilmestep deltaT is 20 s.
> 
> Thanks very much!!
> Yanhong
> 
> Below is my data file:
> # ====================
> # | Model parameters |
> # ====================
> #
> # Continuous equation parameters
>   &PARM01
> # tRef= 18.8, 16.3, 13.1, 10.4, 8.1, 6.0, 4.5,
> #      3.4, 2.7, 2.2, 1.8, 1.5, 1.2, 1.0, 0.9,
>   tRefFile='T0solid_diffusion_160x72.bin',
> # tRef=44*1600.,
>   sRef= 44*34.7,
>   cosPower=1.,
>   viscAr=1.E-3,
>   viscAh=12.E5,
>   no_slip_sides=.FALSE.,
>   no_slip_bottom=.TRUE.,
>   bottomDragLinear=1.E-3,
> #diffK4T=2.E12,
>   diffKhT=1.E3,
>   diffKrNrT=44*1.E-4,
>   ivdc_kappa=100.,
>   implicitDiffusion=.TRUE.,
> # eosType='JMD95Z',
>   eosType='LINEAR',
>   tAlpha=4.E-5,
>   sBeta =0.E-4,
>   saltStepping=.FALSE.,
>   gravity=22,
>   rhonil=3300.,
>   rhoConst=2600.,
>   HeatCapacity_Cp=1800.,
>   implicitFreeSurface=.TRUE.,
>   nonlinFreeSurf=4,
>   select_rStar=2,
>   hFacInf=0.2,
>   hFacSup=2.0,
>   exactConserv=.TRUE.,
>   staggerTimeStep=.TRUE.,
>   useCDscheme=.TRUE.,
>   readBinaryPrec=64,
>   tempAdvScheme=77,
> # usePickupBeforeC54=.TRUE.,
>   rotationPeriod=69120.,
> # useCoriolis=.FALSE.,
>   Tsolidus=1700.,
>   Tliquidus=2000.,
>   &
> 
> # Elliptic solver parameters
>   &PARM02
>   cg2dMaxIters=1000,
> #cg2dTargetResidual=1.E-13,
>   cg2dTargetResWunit=1.E-17,
>   &
> 
> # Time stepping parameters
>   &PARM03
>   niter0=0,
>   nTimeSteps=20000000,
> #endTime=3110400000.,
>   deltaT=10.0,
> # deltaTmom=100.0,
> # deltaTfreesurf=2000.0,
> # deltaTtracer=600.0,
> # deltaTClock =600.0,
>   forcing_In_AB=.FALSE.,
>   abEps=0.1,
>   tauCD=321428.,
>   tauThetaClimRelax=2000.0,
> # pickupStrictlyMatch=.FALSE.,
>   chkptFreq=0.0,
>   pChkptFreq=5000000.0,
>   taveFreq=0.0,
>   dumpFreq=5000000.0,
>   diagFreq=31104000000.0,
>   monitorFreq=31104000000.0,
> # monitorFreq=1.0,
>   monitorSelect=2,
>   &
> 
> # Gridding parameters
>   &PARM04
>   usingSphericalPolarGrid=.TRUE.,
> # delRc= 20.,  60.,  85., 120., 165., 215., 265., 315.,
> #       365., 415., 465., 515., 565., 615., 665., 350.,
> # delRcFile='delRc.bin',
>   delR= 10., 10., 10., 10., 10., 10., 10., 10., 10., 10., 20., 20., 20., 
> 20., 20., 20.,
>          40., 40., 40., 40., 40., 60., 60., 60., 60., 80., 80., 80., 
> 100., 100., 100., 100.,
>          100., 150., 150., 200., 200., 200., 200., 200., 300., 300., 
> 300., 400.,
>   rSphere=9E6,
>   ygOrigin=-81.,
>   xgOrigin=-180,
>   delY=72*2.25,
>   delX=160*2.25,
>   &
> 
> # Input datasets
>   &PARM05
>   bathyFile='topo3D_160x72_5400m_4walls.bin',
> # zonalWindFile='taux_Az1E-5mod_160x72.bin',
> # meridWindFile='tauy_Az1E-5mod_160x72.bin',
>   thetaClimFile='sst3D_mod_160x72.bin',
>   &
> 
> 
> 
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-- 
Christoph Völker
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
Am Handelshafen 12
27570 Bremerhaven

+49 (0)471-4831-1848
christoph.voelker at awi.de
https://orcid.org/0000-0003-3032-114X