[MITgcm-support] how to change the vertical mixing strength

[Martin Losch]

Hi Fei,

I think this is so because you are already prescribing a diffusion coefficient **field** at the bottom of your namelist file:

 diffKrFile='total_diffkr_r009bit11.bin’,

I assume that this file contains values that are locally already larger than whatever you specify for diffKrT/S

Repeat your experiment without the diffKrFile (but then your overturning will probably break down first).

Martin


> On 20. Dec 2019, at 15:33, 979583702 <979583702 at qq.com> wrote:
> 
> Hi everyone,
> 
> Recently, I'd like to study the relationship between MOC and ocean vertical mixing. I want to change the strength of vertical mixing, as far as I know, we can change the two parameters:  diffKrT and  diffKrS (the value typically ranges from 1.E-5 to 1.E-4) in the data file. In my experiments, I changed diffKrT and  diffKrS from 1.E-5 to 5.E-5, but I found there is little change in the MOC strength. It seems quite odd.
> 
> In addition, I didn't switch on the KPP package in the data.pkg. (I comment out the line #useKPP = .TRUE. in data.pkg)
> 
> I was wondering if anyone could tell me the reason why MOC changes little when I change the  diffKrT and  diffKrS.  Is there any better way to change the vertical mixing strength (e.g., switch on KPP package and change the vertical mixing strength)?  If there is, how to change?
> 
> Thank you so much.
> 
> Best,
> 
> Fei
> 
> 
> 
> Here is my data file:
> # ====================
> # | Model parameters |
> # ====================
> #
> # Continuous equation parameters
>  &PARM01
>  tRef               = 3*23.,3*22.,21.,2*20.,19.,2*18.,17.,2*16.,15.,14.,13.,
>                       12.,11.,2*9.,8.,7.,2*6.,2*5.,3*4.,3*3.,4*2.,12*1.,
>  sRef               = 50*34.5,
>  no_slip_sides  = .TRUE.,
>  no_slip_bottom = .TRUE.,
> #
>  viscAr=0.5E-4,
> #
>  viscAh=1.E0,
>  viscAhGrid=2.E-2,
> # viscAh=2.0e4,
> #
>  diffKhT=1.E1,
>  diffKhS=1.E1,
> # change the vertical mixing parameters from 1.E-5 to 5.E-5
>  diffKrT=1.E-5,
>  diffKrS=1.E-5,
> #
> ### diffKrBL79surf=0.1E-4,
> ### diffKrBL79deep=1.0E-4,
>  bottomDragQuadratic = 0.001,
> #when using ggl90
>  ivdc_kappa=10.,
>  implicitDiffusion=.TRUE.,
>  implicitViscosity=.TRUE.,
>  useRealFreshWaterFlux=.TRUE.,
> # balanceThetaClimRelax=.TRUE.,
>  balanceSaltClimRelax=.TRUE.,
> # balanceEmPmR=.TRUE.,
> # balanceQnet=.TRUE.,
>  allowFreezing=.FALSE.,
> ### hFacInf=0.2,
> ### hFacSup=2.0,
>  hFacMin=.2,
>  hFacMinDr=5.,
>  select_rStar=2,
>  nonlinFreeSurf=4,
>  gravity=9.81,
>  rhonil=1029.,
>  rhoConst=1029.,
>  rhoConstFresh=1000.,
>  convertFW2Salt=-1.,
>  eosType='JMD95Z',
>  implicitFreeSurface=.TRUE.,
>  exactConserv=.TRUE.,
>  useSingleCpuIO=.TRUE.,
>  tempAdvScheme=30,
>  saltAdvScheme=30,
>  tempVertAdvScheme=3,
>  saltVertAdvScheme=3,
>  tempImplVertAdv=.TRUE.,
>  saltImplVertAdv=.TRUE.,
>  staggerTimeStep=.TRUE.,
>  vectorInvariantMomentum=.TRUE.,
> #when using the cd scheme:
> # useCDscheme=.TRUE.,
>  useJamartWetPoints=.TRUE.,
>  readBinaryPrec=32,
>  writeBinaryPrec=32,
>  debugLevel=1,
>  /
> 
> # Elliptic solver parameters
>  &PARM02
>  cg2dMaxIters=300,
> #cg2dTargetResWunit=1.E-12,
>  /
> 
> # Time stepping parameters
>  &PARM03
>  nIter0=0,
> #2 lev2 for testing:
> #nTimeSteps=8,
>  nTimeSteps=350000,
> #
>  forcing_In_AB=.FALSE.,
>  momDissip_In_AB=.FALSE.,
> #when using the cd scheme:
> # epsAB_CD = 0.25,
> # tauCD=172800.0,
>  deltaTmom   =3600.,
>  deltaTtracer=3600.,
>  deltaTfreesurf=3600.,
>  deltaTClock =3600.,
> #when using ab2:
> # abEps = 0.1,
> #when using ab3:
>  doAB_onGtGs=.FALSE.,
>  alph_AB=0.5,
>  beta_AB=0.281105,
> #
>  pChkptFreq  =10368000.0,
>  chkptFreq   =10368000.0,
> # taveFreq    =2635200.0,
> # dumpFreq    =2635200.0,
> # monitorFreq = 7200.0,
>  monitorFreq = 2592000.0,
>  dumpInitAndLast = .TRUE.,
>  adjDumpFreq = 31536000.0,
> #adjDumpFreq = 604800.0,
>  adjMonitorFreq = 864000.0,
>  pickupStrictlyMatch=.FALSE.,
>  /
> 
> # Gridding parameters
>  &PARM04
>  usingCurvilinearGrid=.TRUE.,
>  delR = 
>      10.00, 10.00, 10.00, 10.00, 10.00, 10.00, 10.00, 10.01,
>      10.03, 10.11, 10.32, 10.80, 11.76, 13.42, 16.04, 19.82, 24.85,
>      31.10, 38.42, 46.50, 55.00, 63.50, 71.58, 78.90, 85.15, 90.18,
>      93.96, 96.58, 98.25, 99.25,100.01,101.33,104.56,111.33,122.83,
>      139.09,158.94,180.83,203.55,226.50,249.50,272.50,295.50,318.50,
>      341.50,364.50,387.50,410.50,433.50,456.50,
>  /
> 
> # Input datasets
>  &PARM05
>  diffKrFile='total_diffkr_r009bit11.bin',
>  adTapeDir='tapes',
> #bathyFile      ='bathy_eccollc_90x50.bin',
>  bathyFile      ='bathy_eccollc_90x50_min2pts.bin',
>  hydrogThetaFile='T_OWPv1_M_eccollc_90x50.bin',
>  hydrogSaltFile ='S_OWPv1_M_eccollc_90x50.bin',
>  viscA4Dfile    ='fenty_biharmonic_visc_v11.bin',
>  viscA4Zfile    ='fenty_biharmonic_visc_v11.bin',
>  geothermalFile='geothermalFlux.bin',
> #
>  /
> 
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