[MITgcm-support] A Request!

Fri Jul 13 02:43:26 EDT 2012

Hi Abhisek,

I guess so far nobody answered your question because 
a. you asked a very unspecific question
b. the files that you attached where in a propriatory format (e.g. I had no way of extracting them)
c. people are annoyed about large attachments to this list
I recommend that in the future you put the data you want others to see on a web-server and provide a link and ask more specific question and your success with the list will be higher.

In general, the various MITgcm-verification experiments are not necessarily tuned up to give the best possible solution. "We" leave that to the user. Having said that, the global_ocean.90x40x15 (or tutorial_global_oce_latlon which is almost the same), usually run into a fairly realistic state (it took quite some time to tune this configuration). But you cannot take that configuration and simply increase the resolution, instead you'll need to tune it again.

Global ocean modelling is not trivial. I suggest that you talk to your supervisor about what you actually want to study and then set up your experiment. I also suggest that you consult the literature. E.g Griffies et al 2009, Ocean Modelling is a good starting point that gives you an impression on how different models can be and how large model biases usually are.

My general remark is that restoring to salinity and providing a fresh water flux at  the same time is probably not a good idea (in my experience). Other parameters to tune are vertical and horizontal mixing. The GM-parameters also require attention. I am attaching a set of parameters that I used for 2deg similar to yours, but with seaice and different forcing (CORE v1, see GFDL website), but there is no guarantee that these parameters will work for your 1deg configuration, and even for your version of the code (I used that configuration years ago and some parameters have been removed/replaced)

Good luck,

Martin

On Jul 12, 2012, at 5:14 PM, Abhisek Chakraborty wrote:

> Respected Dr. Martin Losch,
> 
> I am using MITgcm global ocean model to study sensitivity of few parameters on some oceanic processes for my Ph.D. work.
> 
> I already have posted this mail to MITgcm forum (mailing list), but till now I didn't get any reply. So out of impatience, I dare sending this mail to you as you are you are one of the experts of this field.
>  
> I have configured MITgcm for global oceans (80S-80N, 0-360deg, 32 vertical levels, 1*1 deg horizontal resolution) and ran it for 100 years using climatological forcings. After completing the run,  when I compared the simulated values (e.g. SST and SSS) with Levitus climatology, I found a huge overestimation by the model. The 'data' file I used for my simulation is:
> 
> # ******************************
> # Model parameters
> # Continuous equation parameters
> # ******************************
>  &PARM01
>  tRef= 25.0,24.5,24.0 , 23.5, 23.0 ,22.5, 22.0 , 21.5,21.0 ,20.5, 20.0 ,
>        19.5, 19.0 , 18.5, 18.0 ,17.5, 17.0 , 16.0 , 15.0 ,
>        14.0 , 13.0 , 12.0 , 11.0 , 10.0 ,
>         9.0 ,  8.0 ,  7.0 ,  6.0,   5.0 ,
>         4.0 ,  3.0 ,  2.0 ,
>  sRef=34.58, 34.62, 34.68, 34.72, 34.73, 
>        34.65, 34.75, 34.82, 34.87, 34.90,
>        34.90, 34.86, 34.78, 34.69, 34.60,
>        34.58, 34.62, 34.68, 34.72, 34.73,
>        34.74, 34.73, 34.73, 34.72, 34.72,
>        34.71, 34.70, 34.69,34.78, 34.69, 34.60,34.72,
>  no_slip_sides=.false.,
>  no_slip_bottom=.TRUE.,
>  viscAr=1.E-4,
>  viscAh=1.E2,
>  diffKhT=0.0,
>  diffKrT=3.E-5,
>  diffKhS=0.0,
>  diffKrS=3.E-5,
>  rhonil=1035.,
>  rhoConstFresh=1000.,
>  beta=1.E-11,
>  tAlpha=2.E-4,
>  sBeta =7.4E-4,
>  gravity=9.81,
>  gBaro=9.81,
>  rigidLid=.FALSE.,
>  implicitFreeSurface=.true.,
>  eosType='JMD95Z',
>  ivdc_kappa=100.,
>  implicitDiffusion=.TRUE.,
>  allowFreezing=.TRUE.,
>  exactConserv=.TRUE.,
>  useRealFreshWaterFlux=.TRUE.,
>  useCDscheme=.TRUE.,
>  readBinaryPrec=32,
>  writeBinaryPrec=32,
>  hFacMin=0.05,
>  hFacMinDr = 50,
>  useSingleCpuIO =.TRUE.,
>  globalFiles = .TRUE.,
>  &
> 
> # **************************
> # Elliptic solver parameters
> # **************************
>  &PARM02
>  cg2dMaxIters=500,
>  cg2dTargetResidual=1.E-13,
>  &
> 
> # ************************
>  Time stepping parameters
> # ************************
>  &PARM03
> # nIter0=      18000,
> # nTimeSteps = 27000,
> # 100 years of integration will yield a reasonable flow field
>  startTime = 0.,
>  endTime   = 3110400000.,
>  deltaTmom = 100.,
>  tauCD =     321428.,
>  deltaTtracer= 43200.,
>  deltaTClock = 86400.,
>  deltaTfreesurf= 172800.,
>  abEps = 0.1,
>  pChkptFreq= 2592000.,
>  dumpFreq=   2592000.,
>  taveFreq=   2592000.,
>  monitorFreq=2592000.,
> # 2 months restoring timescale for temperature
>  tauThetaClimRelax= 5184000.,
> # 6 months restoring timescale for salinity
>  tauSaltClimRelax = 15552000.,
>  periodicExternalForcing=.TRUE.,
>  externForcingPeriod=2592000.,
>  externForcingCycle=31104000.,
>  &
> 
> # Gridding parameters
>  &PARM04
>  usingSphericalPolarGrid=.TRUE.,
>  delR= 10.,10.,20., 25.,25.,25.,25.,50.,50.,
>        50.,100.,100.,100.,100.,100.,100.,100.,100.,100.,100.,
>        100.,100.,250.,250.,500.,500.,500.,500.,500.,500.,500.,500.,  
> ygOrigin=-80.,
> xgOrigin=0.0,
> dySpacing=1.,
> dxSpacing=1.,
> &
> 
> # Input datasets
>  &PARM05
>  bathyFile=      'ETOPO2.BIN',
>  hydrogThetaFile='LEV_T.BIN',
>  hydrogSaltFile= 'LEV_S.BIN',
>  zonalWindFile=  'TAUX.BIN',
>  meridWindFile=  'TAUY.BIN',
>  thetaClimFile=  'SST.BIN',
>  saltClimFile=   'SSS.BIN',
>  surfQFile=      'QNET.BIN',
>  the_run_name=   'global_oce_latlon',
> # fresh water flux is turned on, comment next line to it turn off
> # (maybe better with surface salinity restoring)
>   EmPmRFile=      'EMP.BIN',
> &
> 
> The 'packages.conf' files is
> #
> #  $Header: /u/gcmpack/MITgcm/verification/tutorial_global_oce_latlon/code/packages.conf,v 1.3 2009/06/29 01:58:27 jmc Exp $
> #  $Name: checkpoint63m $
> #
> 
> gfd
> gmredi
> cd_code
> timeave
> ptracers
> mnc
> 
> The MONTHLY PLOTS (1:Jan, 2: Feb etc.)  of simulation and corresponding LEVITUS values are attached here for 12 months (after 100years). Also the PLOT of time averaged Kinetic Energy is attached. 
> 
> Can your good self please look into the attached results and guide me to correct my simulations? This is very much important for me before proceeding further with MITgcm.
> 
> Looking for you kind guidance and thanking in advance,
> 
> yours humbly,
> Abhisek Chakraborty
> Ahmedabad, India
> <overestimation.tar.gz>
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