[MITgcm-support] Warning and time stepping issue

Thu Jan 16 10:41:43 EST 2014

Hi Anthony,

I usually find the stability “analysis” in the tutorials quite illustrative. For example, for the 4deg global ocean experiment <http://mitgcm.org/public/r2_manual/latest/online_documents/node129.html>, you can find  a couple of stability criteria: CFL for advection and viscosity, but also for inertial oscillations. The Coriolis is treated explicitly and I believe, that this limits your time step for the momentum equations. The only way around it is to use asynchronous time stepping (at the usual cost of distorted physics).

Martin

On Jan 16, 2014, at 10:13 AM, Anthony Coletti <ajcolett at geo.umass.edu> wrote:

> I should be more specific with my problem.  Apologies.
> 
> See below for the original problem:
> 
> I am using the sea-ice package and external forcing packages (along with other default packages) to do a control LGM simulation of the Arctic.  I am currently trying to see how much sea ice I can grow in the Arctic during this period.  I have prescribed most of the atmosphere, the initial SST and Salinity fields.
> 
> My data file looks like this:
> 
> # ====================
> # | Model parameters |
> # ====================
> #
> # Continuous equation parameters
>  &PARM01
>  tRef=15*20.,
>  sRef=15*35.,
>  viscAh =3.E5,
>  viscAr =1.E-3,
>  diffKhT=0.,
>  diffK4T=0.,
>  diffKrT=3.E-5,
>  diffKhS=0.,
>  diffK4S=0.,
>  diffKrS=3.E-5,
>  ivdc_kappa=10.,
>  implicitDiffusion=.TRUE.,
>  gravity=9.81,
>  rhoConst=1035.,
>  rhoConstFresh=1000.,
>  eosType='JMD95Z',
>  staggerTimeStep=.TRUE.,
>  vectorInvariantMomentum=.TRUE.,
>  implicitFreeSurface=.TRUE.,
>  exactConserv=.TRUE.,
>  select_rStar=2,
>  nonlinFreeSurf=4,
>  hFacInf=0.2,
>  hFacSup=2.0,
>  useRealFreshWaterFlux=.TRUE.,
>  hFacMin=.1,
>  hFacMinDr=20.,
> #- to check that it has no impact:
> # doResetHFactors=.TRUE.,
> # tempAdvScheme=7,
> # saltAdvScheme=7,
>  readBinaryPrec=32,
>  writeBinaryPrec=32,
>  useSingleCpuIO=.TRUE.,
>  &
> 
> # Elliptic solver parameters
>  &PARM02
>  cg2dMaxIters=200,
> #cg2dTargetResidual=1.E-9,
>  cg2dTargetResWunit=1.E-14,
>  &
> 
> # Time stepping parameters
>  &PARM03
>  nIter0=0.,
>  endTime=31557600000.,
>  deltaT= 1500.,
>  abEps = 0.1,
>  forcing_In_AB=.FALSE.,
>  pickupStrictlyMatch=.FALSE.,
>  cAdjFreq=0.,
>  pChkptFreq   = 31557600.,
>  chkptFreq    = 15778800.,
>  monitorFreq = 21600.,
>  &
> 
> # Gridding parameters
>  &PARM04
>  usingCurvilinearGrid=.TRUE.,
>  horizGridFile='../../../input.files/grid_inputs/grid_cs32',
>  delR= 50., 70., 100., 140., 190.,
>        240., 290., 340., 390., 440.,
>        490., 540., 590., 640., 690.,
>  &
> 
> # Input datasets
>  &PARM05
>  bathyFile      ='../../../input.files/LGM_cntr/lgm+ish_cntr_bathy.bin',
>  hydrogThetaFile='../../../input.files/LGM_cntr/sfc_T_coldstart_32x32x15.bin',
>  hydrogSaltFile ='../../../input.files/LGM_cntr/oce_salt_coldstart_32x32x15.bin',
>  &
> 
> 
> When I lower my time step BELOW 5000. s, it does not crash and is stable the entire run.  I also have bathymetry set to LGM levels (adding 120m to the bathymetry files) to make the ocean more shallow.
> 
> 
> Anthony
> 
> 
> Anthony J. Coletti
> Climate System Research Center
> Department of Geosciences
> Morrill Building
> 611 N. Pleasant Street
> 233 Morrill Science Center
> University of Massachusetts-Amherst
> paleoclimate.org
> Email: ajcolett at geo.umass.edu
> http://blogs.umass.edu/ajcolett/
> 
> “For me, I am driven by two main philosophies: know more today about the world than I knew yesterday and lessen the  suffering of others. You'd be surprised how far that gets you.” ― Neil deGrasse Tyson
> 
> 
> 
> 
> On Jan 16, 2014, at 9:45 AM, Anthony Coletti <ajcolett at geo.umass.edu> wrote:
> 
>> Hi all,
>> 
>> I am trying to run a course 32x32x15 (6 faces) run to get some preliminary data.  Unfortunately, my time step will not exceed 5000.s.  ~ Two minutes into the run, it crashes and I get the corresponding error::
>> 
>> WARNING: r*FacC > hFacSup at       1 pts : bi,bj,Thid,Iter=   4   1   1       106
>>  e.g. at i,j=   2   1 ; rStarFac,H,eta =  2.028435  2.200000E+01  2.262556E+01
>> WARNING: r*FacC > hFacSup at       1 pts : bi,bj,Thid,Iter=   4   1   1       107
>>  e.g. at i,j=   2   1 ; rStarFac,H,eta =  2.333596  2.200000E+01  2.933912E+01
>> WARNING: r*FacW < hFacInf at       2 pts : bi,bj,Thid,Iter=   2   1   1       108
>>  e.g. at i,j=   5   2 ; rStarFac,H,eta =  0.094709  1.368000E+03 -6.740896E+02 -1.803211E+03
>> STOP in CALC_R_STAR : too SMALL rStarFacW !
>> WARNING: r*FacS < hFacInf at       1 pts : bi,bj,Thid,Iter=   2   1   1       108
>>  e.g. at i,j=   3   2 ; rStarFac,H,eta = -0.186928  2.400000E+02  5.703576E+01 -6.277609E+02
>> STOP in CALC_R_STAR : too SMALL rStarFacS !
>> WARNING: r*FacC < hFacInf at       2 pts : bi,bj,Thid,Iter=   2   1   1       108
>>  e.g. at i,j=   5   2 ; rStarFac,H,eta = -0.152948  1.564000E+03 -1.803211E+03
>> STOP in CALC_R_STAR : too SMALL rStarFacC !
>> 
>> If you need any other info, please let me know.  Any help would be appreciated!
>> 
>> 
>> Thanks!
>> 
>> Anthony
>> 
>> Anthony J. Coletti
>> Climate System Research Center
>> Department of Geosciences
>> Morrill Building
>> 611 N. Pleasant Street
>> 233 Morrill Science Center
>> University of Massachusetts-Amherst
>> paleoclimate.org
>> Email: ajcolett at geo.umass.edu
>> http://blogs.umass.edu/ajcolett/
>> 
>> “For me, I am driven by two main philosophies: know more today about the world than I knew yesterday and lessen the  suffering of others. You'd be surprised how far that gets you.” ― Neil deGrasse Tyson
>> 
>> 
>> 
>> 
> 
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