[MITgcm-support] NaNs in output

[Martin Losch]

The model becomes numerically unstable (and this can happen after some time, if the forcing is variable) and you need to investigate your input parameters (time step, forcing etc.).

I am surprised it runs at all. What is your grid resolution? There is no dx/ySpacing or delX/delY in your PARM04 namelist.
It is also strange that your cg2d: line has zeros for the rhsMax.

Martin

On Oct 1, 2012, at 8:01 AM, Fengchao Yao wrote:

> Dear all,
> 
> The MITgcm I am running is constantly giving NaNs after a couple years of stable running.  Below is the information from the STDOUT file where the NaNs occur. Anybody has some idea on how to handle this? Thanks for your help.
> 
> Fengchao
> 
> STDOUT:
> --------------------------------------------------------------------------------------------------------------
> cg2d: Sum(rhs),rhsMax =   7.95491814529655E+03  0.00000000000000E+00
> cg2d: Sum(rhs),rhsMax =   7.95490803828502E+03  0.00000000000000E+00
> SURF_ADJUSTMENT: Iter=   3348930 Nb_pts,Vol=         1  7.60072406E+06
> cg2d: Sum(rhs),rhsMax =   7.95489793127349E+03  0.00000000000000E+00
> SURF_ADJUSTMENT: Iter=   3348931 Nb_pts,Vol=         5  1.96015022E+08
> cg2d: Sum(rhs),rhsMax =  -1.77088743107612E+21  0.00000000000000E+00
> SURF_ADJUSTMENT: Iter=   3348932 Nb_pts,Vol=    128878  6.73412758E+43
> cg2d: Sum(rhs),rhsMax =                    NAN  0.00000000000000E+00
> cg2d: Sum(rhs),rhsMax =                    NAN                   NAN
> cg2d: Sum(rhs),rhsMax =                    NAN                   NAN
> cg2d: Sum(rhs),rhsMax =                    NAN                   NAN
> cg2d: Sum(rhs),rhsMax =                    NAN                   NAN
> cg2d: Sum(rhs),rhsMax =                    NAN                   NAN
> cg2d: Sum(rhs),rhsMax =                    NAN                   NAN
> cg2d: Sum(rhs),rhsMax =                    NAN                   NAN
> 
> 
> data file
> -------------------------------------------------------------------------------------------------------------
> &PARM01
> tRef               = 3*23.,3*22.,21.,2*20.,19.,2*18.,17.,2*16.,15.,14.,13.,
>                      12.,11.,2*9.,8.,7.,6.,
> sRef               = 25*38,
> no_slip_sides=.FALSE.,
> no_slip_bottom=.TRUE.,
> 
> viscAh = 3.0e1,
> 
> viscA4 = 0e7,
> viscAhGrid = 0.00,
> 
> viscA4Grid = 0.03,
> 
> viscAr = 7.E-4,
> 
> diffK4T=0e7,
> diffK4S=0e7,
> diffKrT=1.E-5,
> diffKrS=1.E-5,
> diffKrBL79surf=0.1E-4,
> diffKrBL79deep=1.0E-4,
> bottomDragQuadratic= 0.002,
> implicitDiffusion=.TRUE.,
> implicitViscosity=.TRUE.,
> gravity=9.81,
> rhonil=1029.,
> rhoConstFresh=1000.,
> eosType='JMD95Z',
> staggerTimeStep=.TRUE.,
> vectorInvariantMomentum=.TRUE.,
> useEnergyConservingCoriolis=.true.,
> implicitFreeSurface=.TRUE.,
> exactConserv=.TRUE.,
> useSingleCpuIO=.TRUE.,
> tempAdvScheme=30,
> saltAdvScheme=30,
> nonlinFreeSurf=1,
> useRealFreshWaterFlux=.FALSE.,
> allowFreezing=.false.,
> hFacMin=.3,
> hFacMinDr=30.,
> readBinaryPrec=64,
> /
> &PARM02
> cg2dMaxIters=5000,
> cg2dTargetResWunit=1.E-11,
> /
> &PARM03
> nIter0=_stTIME_,
> nTimeSteps=_nsteps_,
> deltaT = _delt_,
> pickupStrictlyMatch=.FALSE.,
> cAdjFreq=0.,
> abEps = 0.01,
> forcing_In_AB=.FALSE.,
> pChkptFreq=31104000.0,
> chkptFreq=31104000.0,
> taveFreq=259200.0,
> periodicExternalForcing=.FALSE.
> #dumpFreq=3600.,
> monitorFreq=2635200000.,
> # tauThetaClimRelax= 2592000.,
> # tauSaltClimRelax= 7776000.,
> /
> &PARM04
> usingCurvilinearGrid=.TRUE.,
> delR= 10.2652, 11.8262, 13.6398, 15.7495, 18.2060, 21.0677, 24.4002,
> 28.2749, 32.7643, 37.9348, 43.8340, 50.4735, 57.8103, 65.7382,
> 74.1055, 82.7805, 91.7766,101.4306,112.6418,127.2439,148.7415,
> 183.8161,244.2570,340.5531,442.0510,
> /
> &PARM05
> bathyFile='redsea_bathy_fixed.bin',
> # bathyFile='red2_bathyed-10.bin',
> hydrogThetaFile='lev01_temp.bin',
> hydrogSaltFile='lev01_salt.bin',
> zonalWindFile ='uf_198002.data',
> meridWindFile='vf_198002.data',
> surfQFile='qf_198002.data',
> EmPmRFile='ef_198002.data',
> surfQswFile='qsf_198002.data',
> /
> 
> 
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