[MITgcm-support] synchronous vs asynchronous integrations

Samar Khatiwala spk at ldeo.columbia.edu
Fri Jun 2 12:49:41 EDT 2006


David

Not sure why you expect the two to give similar results, especially  
with seasonal forcing.
(See papers by Danabasoglu and Danabasoglu & McWilliams.)
My experience is that the extent to which they differ is (at the very  
least) a function of the
resolution, advection scheme, and the ratio of tracer to momentum  
time steps. Of course,
you should only be comparing the final equilibrium solutions, and not  
some intermediate
transient solution. I take it you haven't run it long enough to spin  
up your model to equilibrium.
There is a long exchange on this topic between myself and Martin  
Losch on the mitgcm-support
list.

Samar

On Jun 2, 2006, at 11:40 AM, David Wang wrote:

> Hello,
>
> I ran two model runs with the same configuration, the same initial  
> fields and the same surface forcing fields, but different timesteps  
> (one is sychronous: deltaT = 3600s; another is asynchronous:  
> deltaTmom = 900s, deltaTtracer = deltrTClock = 10800s). They give  
> considerably different results, which is not what I expected. Of  
> course I prefer the asychronous one since it takes much less  
> integration time, but the differences make me to doubt the  
> integrity of these runs.
>
> The model domain is the tropical pacific. The initial fields are  
> climatological potential temp and salinity. The model is forced by  
> climatological monthly forcings. kpp, gmredi, rbcs packages are used.
>
> I'm attaching my data namelist file and a plot of momKE_ave  
> timeseries over the first model year (which is to show how  
> different they are. blue is the sychronous run and red is the  
> asychronous run). The temperature field snapshots at the end of the  
> first model year also differ, esp. near the equator.
>
> If anyone would have any ideas on what might go wrong, plz let me  
> know. Thanks very much.
>
> - d.
> # ====================
> # | Model parameters |
> # ====================
> #
> # Continuous equation parameters
>  &PARM01
> tRef = 25.95, 25.85, 25.70, 25.41, 25.02,
>        24.56, 24.00, 23.45, 22.84, 22.23,
>        21.61, 20.99, 20.38, 19.77, 19.17,
>        18.56, 17.86, 16.91, 15.74, 14.44,
>        13.09, 11.74, 10.27,  8.90,  7.64,
>         6.61,  5.82,  5.18,  4.63,  4.21,
>         3.84,  3.51,  3.22,  2.91,  2.59,
>         2.24,  1.95,  1.71,  1.54,  1.36,
>         1.22,  1.10,  1.02,  0.95,  0.92,
> #
>  sRef = 45*35.,
> #
>  viscA4  = 1.E13,
>  viscAz  = 1.E-4,
>  diffKhT = 0.E3,
>  diffKzT = 5.E-6,
>  diffKhS = 0.E3,
>  diffKzS = 5.E-6,
> #
>  rhoNil =   1025.,
>  gravity =  9.81,
>  eosType = 'LINEAR',
>  tAlpha = 2.E-4,
>  sBeta =  7.4E-4,
> #
>  rigidLid =            .FALSE.,
>  implicitFreeSurface = .TRUE.,
>  no_slip_bottom     =  .TRUE.,
>  no_slip_sides      =  .TRUE.,
> #
> # ivdc_kappa=10.,
>  implicitDiffusion=.TRUE.,
>  implicitViscosity=.TRUE.,
> #
> # turn on looped cells
>  hFacMin=0.05,
>  readBinaryPrec=32,
> #
>  &
>
> # Elliptic solver parameters
>  &PARM02
>  cg2dMaxIters=1000,
>  cg2dTargetResidual=1.E-13,
>  &
>
> # Time stepping parameters
>  &PARM03
> #
>  startTime  =   0.,
>  endTime    =   31104000.,
> #
>  deltaT =         3600.,
> # deltaTmom =      900.,
> # deltaTtracer =   10800.,
> # deltaTClock  =   10800.,
> #
>  abEps = 0.1,
>  pChkptFreq =  0.,
>  chkptFreq =   0.,
>  monitorFreq = 86400.,
>  dumpFreq = 0.,
>  dumpInitAndLast = .TRUE.,
> #
> # cAdjFreq = -1.,
> #
> # 1 months restoring timescale for surface temperature
> # 2 months restoring timescale for surface salinity
> #
>  tauSaltClimRelax =    5184000.,
>  tauThetaClimRelax =   2592000.,
>  periodicExternalForcing = .TRUE.,
>  externForcingPeriod = 2592000.,
>  externForcingCycle =  31104000.,
>  &
>
> # Gridding parameters
>  &PARM04
>  usingCartesianGrid =      .FALSE.,
>  usingSphericalPolarGrid = .TRUE.,
> #
>  delX = 160*1.,
> #
> delY =       1.0000000,  1.0000000,  1.0000000,  0.9998741,
>  0.9956741,  0.9835052,  0.9675407,  0.9441032,  0.9175377,
>  0.8843880,  0.8491249,  0.8084641,  0.7670174,  0.7215805,
>  0.6768684,  0.6297283,  0.5849037,  0.5392418,  0.4974575,
>  0.4563580,  0.4205704,  0.3867931,  0.3595371,  0.3353481,
>  0.3185692,  0.3055687,  0.3004913,  0.2995090,  0.3004913,
>  0.2995071,  0.3004932,  0.2995071,  0.3004932,  0.2995071,
>  0.3004913,  0.2995090,  0.3004913,  0.2995090,  0.3004904,
>  0.2995100,  0.3004894,  0.2995110,  0.3004894,  0.2995100,
>  0.3004904,  0.2995090,  0.3004913,  0.2995090,  0.3004904,
>  0.2995100,  0.3004899,  0.2995100,  0.3004899,  0.2995100,
>  0.3004904,  0.2995095,  0.3004904,  0.2995095,  0.3004906,
>  0.2995093,  0.3004907,  0.2995093,  0.3004907,  0.2995093,
>  0.3004906,  0.2995095,  0.3004904,  0.2995095,  0.3004904,
>  0.2995100,  0.3004899,  0.2995100,  0.3004899,  0.2995100,
>  0.3004904,  0.2995090,  0.3004913,  0.2995090,  0.3004904,
>  0.2995100,  0.3004894,  0.2995110,  0.3004894,  0.2995100,
>  0.3004904,  0.2995090,  0.3004913,  0.2995090,  0.3004913,
>  0.2995071,  0.3004932,  0.2995071,  0.3004932,  0.2995071,
>  0.3004913,  0.2995090,  0.3004913,  0.3055687,  0.3185692,
>  0.3353481,  0.3595371,  0.3867931,  0.4205704,  0.4563580,
>  0.4974575,  0.5392418,  0.5849037,  0.6297283,  0.6768684,
>  0.7215805,  0.7670174,  0.8084641,  0.8491249,  0.8843880,
>  0.9175377,  0.9441032,  0.9675407,  0.9835052,  0.9956741,
>  0.9998741,  1.0000000,  1.0000000,  1.0000000,  1.0000000,
> #
>  delZ = 10.00, 10.00, 10.00, 10.00, 10.00,
>         10.00, 10.00, 10.00, 10.00, 10.00,
>         10.00, 10.00, 10.00, 10.00, 10.00,
>         11.13, 14.46, 19.82, 26.94, 35.48,
>         44.99, 55.00, 65.01, 74.52, 83.06,
>         90.18, 95.54, 98.87, 100.00, 100.00,
>         100.00, 100.00, 111.42, 143.93, 192.60,
>         250.00, 307.40, 356.07, 388.58, 400.00,
>         400.00, 400.00, 400.00, 400.00, 400.00,
> #
>  phiMin = -29.,
>  thetaMin = 130.,
>  &
>
> # Input datasets
>  &PARM05
>  bathyFile=      '/data1/fats/dwang/myexps/trop_pacific/input/1x3rd/ 
> bathymetry.bin',
>  hydrogThetaFile='/data1/fats/dwang/myexps/trop_pacific/input/1x3rd/ 
> woa01_init_theta.bin',
>  hydrogSaltFile= '/data1/fats/dwang/myexps/trop_pacific/input/1x3rd/ 
> woa01_init_salt.bin',
>  zonalWindFile=  '/data1/fats/dwang/myexps/trop_pacific/input/1x3rd/ 
> dasilva94_monthly_taux.bin',
>  meridWindFile=  '/data1/fats/dwang/myexps/trop_pacific/input/1x3rd/ 
> dasilva94_monthly_tauy.bin',
>  thetaClimFile=  '/data1/fats/dwang/myexps/trop_pacific/input/1x3rd/ 
> woa01_monthly_sst.bin',
>  saltClimFile=   '/data1/fats/dwang/myexps/trop_pacific/input/1x3rd/ 
> woa01_monthly_sss.bin',
>  surfQnetFile=   '/data1/fats/dwang/myexps/trop_pacific/input/1x3rd/ 
> dasilva94_monthly_qnet0.bin',
>  the_run_name=   'trop_pacific.160x124x45',
> #
>  &
> <momKE.png>
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