[MITgcm-support] Reducing Runtime for High Resolution Model

[Nadav Mantel]

Hi everyone,[image: ltp|17404872536696102]


I am attempting to run a high-resolution model of the Gulf of Aqaba. We are
attempting to simluate a desalination plant's long term effects, but the
addmass on a coarse grid doesn't simulate the salt plume as a singular
point increases the salinity of a cell only slightly. Therefore, we
increased the horizontal grid resolution to 60x60 meters, with 32 depth
levels with depths ranging from 5 meters to 255 meters.  Due to the high
resolution, the CFL requires a maximum timestep of 30 sec before the model
crashes. We want to run a hydrostatic simulation for two years which will
result in a very long simulation.

Does anyone have any tips on how to reduce runtime? We tried to increase
the timestep by changing the A4 and Ah max values and also use useFullLeith
but they didn't really help.

Below is our data file, we also use the KPP package if that makes a
difference.

Thanks,
Nadav


 &PARM01

 tRef               =
25.1802,25.0046,24.5519,23.8771,23.3200,22.8004,22.4412,22.2013,22.0148,21.8971,21.8289,21.7756,21.7318,21.6987,21.6644,21.6436,21.6331,21.6271,21.6216,21.6149,21.6078,21.5973,21.5984,21.5975,21.5944,21.5897,21.5834,21.5821,21.5821,21.5821,21.5821,21.5821,

 sRef               =
40.3499,40.3473,40.3498,40.3558,40.3449,40.3549,40.3713,40.3862,40.4040,40.4214,40.4385,40.4526,40.4659,40.4809,40.4995,40.5211,40.5407,40.5525,40.5559,40.5590,40.5621,40.5655,40.5687,40.5719,40.5761,40.5825,40.5909,40.5933,40.5933,40.5933,40.5933,40.5933,

 viscAh             = 0.,

 viscAz             = 5.e-4,

 diffKzT            = 1.e-5,

 diffKzS            = 1.e-5,

 viscA4             = 0.,

 diffKhT            = 0.,

 diffKhS            = 0.,

 viscC2smag         = 2.5,

 viscAhGridMax      = 0.5,

 f0                 = 7.22E-5,

 beta               = 0.,

 gravity            = 9.81,

 gBaro              = 9.81,

 convertFW2Salt     = -1.,

 rigidLid           = .FALSE.,

 implicitFreeSurface= .TRUE.,

 implicitDiffusion  = .TRUE.,

 useCDscheme        = .FALSE.,

 useJamartWetPoints = .TRUE.,

 eosType            = 'MDJWF',

 implicitViscosity  = .TRUE.,

 no_slip_bottom     = .TRUE.,

 no_slip_sides      = .FALSE.,

 bottomDragQuadratic=  2e-3,

 nonHydrostatic     = .FALSE.,

 tempAdvScheme      = 33,

 saltAdvScheme      = 33,

 staggerTimeStep    = .true.,

 hFacMin            =.05,

 hFacMindz          = 10.,

 readBinaryPrec     = 64,

 debuglevel         = 1,

# globalFiles        = .TRUE.,

 useSingleCpuIO     = .TRUE.,

 salt_addMass       = 100,

 selectAddFluid     = 1,

 &


# Elliptic solver parameters

 &PARM02

 cg2dMaxIters        = 200,

 cg2dTargetResidual  = 1.E-12

cg3dMaxIters        = 300,

 cg3dTargetResidual  = 1.E-8,

 &


# Time stepping parameters

 &PARM03

 nIter0=0,

 nTimeSteps=1728, (Note that this is a test run and not the 2 years)

 deltaT=30.,

 abEps      = 0.1,

 pChkptFreq=31104000.,

 dumpFreq=43200.,

 taveFreq=43200.,

 dumpInitAndLast = .FALSE.,

 periodicExternalForcing = .TRUE.,

 externForcingPeriod = 2592000.0,

 externForcingCycle = 31104000.0,

 tauThetaClimRelax =  259200.0,

 tauSaltClimRelax = 86400.0,

 monitorFreq=0.,

# monitorSelect=3.,

 forcing_in_AB = .FALSE.,

 pickupStrictlyMatch = .FALSE.,

 &


# Gridding parameters

 &PARM04

 usingCartesianGrid      = .TRUE.,

 usingSphericalPolarGrid = .FALSE.,

 delX   = 556*60,

 delY   = 3396*60,

 delZ  = 10, 10, 15, 15, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 30, 30,
30, 30, 30, 30, 30, 30, 30, 30, 50, 70, 100, 130, 170, 220, 240, 270,

 &
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