[MITgcm-support] Seeking Assistance with Numerical Instability in MITgcm Simulation of a Plateau Lake

[唐鸿]

Dear MITgcm Support Team,




I hope this message finds you well. 




I am currently working on a simulation project using the MITgcm to study the dynamic processes of a lake situated on the Tibetan Plateau, which experiences freezing during winter. The lake, located at an altitude of 4200m with a depth of 28m and a maximum width of 38km, presents unique challenges due to the strong radiation on the plateau that leads to noticeable warming of the water beneath the ice.




I am writing to seek your expert advice as I have encountered significant numerical instability in my simulations despite my efforts to adjust model parameters. My current setup is that the horizontal grid size is 500m and the vertical grid size is 1m. I have modified the model time step and drive data time to 100s, but I still encounter serious numerical instability.




 I have attached my data file, which contains the configuration parameters of my model setup.




# ====================
# | Model parameters |
# ====================
#
 &PARM01
 tRef=10*11.,
 sRef=10*0.27,
 no_slip_sides=.FALSE.,
 no_slip_bottom=.TRUE.,
 viscAh=1.E-4,
 viscAr=1.E-4,
 HeatCapacity_Cp=3986.,
 rhoConstFresh=1000.,
 rhoNil=1000.,
 eosType='JMD95Z',
#
 nonHydrostatic=.TRUE.,
 rigidLid=.TRUE.,
 implicitFreeSurface=.FALSE.,
#
 useCoriolis=.FALSE.,
 use3dCoriolis=.FALSE.,
#
 useSingleCpuIO=.TRUE.,
 readBinaryPrec=32,
 writeBinaryPrec=32,
 &


# Elliptic solver parameters
 &PARM02
 cg2dMaxIters=700,
 cg3dMaxIters=100,
 cg2dTargetResidual=1.E-7,
 cg3dTargetResidual=1.E-7,
 cg2dUseMinResSol=1,
 &


# Time stepping parameters
 &PARM03
 abEps=0.1,
 deltaT=100,
 nIter0=0,
 nTimeSteps=315361,
 dumpFreq=86400.,
 chkPtFreq=2592000.,
 pChkptFreq=8640000.,
 monitorFreq=100.,
 &


# Gridding parameters
 &PARM04
 usingCartesianGrid=.TRUE.,
 dXspacing=500.,
 dYspacing=500.,
 delR=10*1.,
 &
# Input datasets
 &PARM05
 bathyFile='Bathy_500m.bin',
 the_run_name='Ngoring_LakeTest_HH',


 &






I would greatly appreciate any suggestions or guidance you could provide to improve the numerical stability of my simulation. Thank you very much for considering my request. I look forward to your valuable insights and suggestions.




Best regards,




Hong Tang

University of Chinese Academy of Sciences


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