[MITgcm-support] Warning and time stepping issue

Christoph Voelker christoph.voelker at awi.de
Thu Jan 16 10:59:20 EST 2014 

Hi Anthony and Martin,

I suspect thta it is not the CFL criterium, but the sea-ice in
conjunction with the nonlinear free surface, under extreme cases of ice
formation. I had a similar isue in some last glacial maximum model runs
that I did, where the free surface code basically complained that the
submerged part of the sea ice got too thick. When that happened I also
got very large negative eta values. There was a not particulaly elegant
trick around it that I don't remember at the moment, I'll check. But
Anthony, maybe you can check your ice thickness? 

Cheers, Christoph

On 1/16/14 4:41 PM, Martin Losch wrote:
> 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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-- 
Christoph Voelker
Alfred Wegener Institute for Polar and Marine Research
Am Handelshafen 12
27570 Bremerhaven, Germany
e: Christoph.Voelker at awi.de
t: +49 471 4831 1848

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