[MITgcm-support] Warning and time stepping issue
Martin Losch
Martin.Losch at awi.de
Thu Jan 16 11:19:03 EST 2014
Hi Anthony,
I suggestion to have a look at verification/global_ocean.cs32x15 again and try these parameters:
deltaTmom =1200.,
deltaTtracer=86400.,
deltaTfreesurf=86400.,
deltaTClock =86400.,
instead of deltaT = 5000.,This will speed up the integration (again at the cost of slowed down gravity waves etc. I refer you to the literature about asynchronous time stepping or “tracer acceleration”)
Martin
On Jan 16, 2014, at 11:14 AM, Anthony Coletti <ajcolett at geo.umass.edu> wrote:
> Hi Christoph and Martin,
>
> Thank you for your responses!
>
> @Martin: I am looking through the manual now to see if I can tweak my run to make it run faster (5000s time step is unbearably slow for such course resolution).
>
> @Christoph: My ice thicknesses are not out of the ordinary at all. I think the thickest amount of ice is about 4 meters thick.
>
> 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 10:59 AM, Christoph Voelker <christoph.voelker at awi.de> wrote:
>
>> 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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