[MITgcm-support] Help me get rid of my noise!
Nicolas Grisouard
nicolas.grisouard at stanford.edu
Wed May 7 16:51:20 EDT 2014
Hi,
Your isopycnal slopes there look very steep, but the image is very
squeezed too. Could it be symmetric instability? It's not supposed to
happen at these scales, but other mixed layer instabilities are
probably inhibited by your 2D configuration so, why not? What's the
sign of the PV there?
Nico.
On Wed 07 May 2014 12:57:26 PM PDT, Ryan Abernathey wrote:
> Thanks for all your suggestions.
> I tried turning on convective adjustment with
> ivdc_kappa=1.0,
> in my data file. I also enabled
> #define ALLOW_GGL90_SMOOTH
> in GGL90_OPTIONS.h
>
> It looks like the high values of W went down a little bit over the
> slope, a slight improvement. So I guess I am satisfied that, as Sonia
> put it, the solution is not "pretty" but is physically correct.
>
> I am still worried about the "stripes" of high and low W within the
> mixed layer between -60 and -50.
>
> Thanks again,
> Ryan
>
>
>
> On Wed, May 7, 2014 at 3:14 PM, David Ferreira <dfer at mit.edu
> <mailto:dfer at mit.edu>> wrote:
>
> Patrick's right, you need to have some convection with ggl90, but
> in case it's not enough: have you tried activating the smoother in
> ggl90 ? Might help too.
> david
>
>
>
> On 5/7/14 7:52 PM, Patrick Heimbach wrote:
>> Ryan,
>>
>> yes, switching on convective adjustment is still advised in conjunction with ggl90 (in contrast to KPP where the non-local term Gamma should take care of this).
>>
>> Cheers
>> p.
>>
>> On May 7, 2014, at 2:43 PM, Ryan Abernathey<ryan.abernathey at gmail.com> <mailto:ryan.abernathey at gmail.com> wrote:
>>
>>> Thanks for all the helpful suggestions everyone!
>>> I am now convinced that this isn't as "unphysical" as I thought.
>>>
>>> In response to Christopher's suggestions, does anyone know whether I should have convective adjustment active together with GGL90? I know for KPP you are supposed to turn off all convective adjustment. Is that also the case for GGL?
>>>
>>> Thanks again,
>>> Ryan
>>>
>>>
>>> On Wed, May 7, 2014 at 2:10 PM, Christopher L. P. Wolfe<christopher.wolfe at stonybrook.edu> <mailto:christopher.wolfe at stonybrook.edu> wrote:
>>>
>>> My guess that you’re seeing hydrostatic convection. You don’t seem to have set either cAdjFreq or ivdc_kappa and my understanding is that they both default to zero. So, your model’s trying to do convection through the momentum equations and the convective scale is smaller than your grid spacing (hydrostatic convection runs to the grid scale).
>>>
>>> Christopher
>>>
>>>
>>> On May 7, 2014, at 1:20 PM, Ryan Abernathey<ryan.abernathey at gmail.com> <mailto:ryan.abernathey at gmail.com> wrote:
>>>
>>>> I guess my image didn't make it through on that last email.
>>>>
>>>>
>>>>
>>>> On Wed, May 7, 2014 at 1:11 PM, Ryan Abernathey<ryan.abernathey at gmail.com> <mailto:ryan.abernathey at gmail.com> wrote:
>>>> Hello MITgcm Support Group,
>>>>
>>>> I am running a 2D model (depth and latitude) in a Southern Ocean configuration. I am trying to eliminate what appears to be unphysical grid-scale noise in my W field--columns of alternately very high and low W. This is a snapshot of W after 5 years of spinup. This pattern is steady in time.
>>>>
>>>> As you can see, the noise is concentrated mainly (but not exclusively) over the shelf break. A possibly related issue is that my cg2d solver is relatively far from convergence:
>>>> cg2d: Sum(rhs),rhsMax = -5.46186194609888E-05 6.64557830841732E-02
>>>>
>>>> My model is 0.5 degree resolution in latitude, meaning that it is relatively high resolution compared to the tutorials (e.g. ideal_2D_oce), but of course it has no eddies or any temporal variability at all, since it is 2D. This puts it in an unknown [at least to me] parameter regime.
>>>>
>>>> I have tried cranking the lateral viscosity (both laplacian and biharmonic) up as high as they will go. I have enabled both linear and quadratic bottom drag. I am NOT using the CD scheme; the noise was much worse with it enabled. I am NOT using KPP but rather GGL90. (I tried with KPP and it was not very different.)
>>>>
>>>> I would appreciate any suggestions you have about how to get rid of this noise and achieve smooth fields.
>>>>
>>>> Thanks,
>>>> Ryan
>>>>
>>>> ####### data file ##########
>>>> &PARM01
>>>> useAreaViscLength=.FALSE.,
>>>> viscAr=1.0E-03,
>>>> viscA4=1e12,
>>>> viscAh=1e5,
>>>> tempAdvScheme=77,
>>>> # KrT fields are read in from a file
>>>> diffKrT=0.0E-5,
>>>> diffKhT=0.0,
>>>> diffK4T=0.0,
>>>> staggerTimeStep=.TRUE.,
>>>> # initial vertical profiles of T and S
>>>> tRef=44*0.0,
>>>> sRef=44*35.0,
>>>> # equation of state
>>>> eosType='LINEAR',
>>>> rhonil=1035.,
>>>> eosType='LINEAR',
>>>> tAlpha=2.000000E-04,
>>>> sBeta=0.000000E+00,
>>>> saltStepping=.FALSE.,
>>>> # boundary conditions
>>>> no_slip_sides=.FALSE.,
>>>> no_slip_bottom=.TRUE.,
>>>> # needed for points above the U sponge layer (shelf)
>>>> bottomDragLinear=1.E-3,
>>>> bottomDragQuadratic = 0.0012
>>>> # additional drag is done with RBCS
>>>> # physical parameters
>>>> gravity=9.810000E+00,
>>>> # implicit diffusion and convective adjustment
>>>> implicitDiffusion=.TRUE.,
>>>> implicitViscosity=.TRUE.,
>>>> implicitFreeSurface=.TRUE.,
>>>> # exact volume conservation
>>>> # exactConserv=.TRUE.,
>>>> # C-V scheme for Coriolis term
>>>> useCDscheme=.FALSE.,
>>>> # partial cells for smooth topography
>>>> hFacMin=5.000000E-02,
>>>> # file IO stuff
>>>> readBinaryPrec=64,
>>>> useSingleCpuIO=.TRUE.,
>>>> debugLevel=1,
>>>> &
>>>> # elliptic solver parameters
>>>> &PARM02
>>>> cg2dMaxIters=500,
>>>> cg2dTargetResidual=1E-09,
>>>> &
>>>> # timestepping parameters
>>>> &PARM03
>>>> nIter0=0000172800,
>>>> # nTimeSteps=1000,
>>>> # nTimeSteps=12961,
>>>> nTimeSteps=345600,
>>>> # deltaT=3600.0,
>>>> # deltaT=2400.,
>>>> # deltaT=1800.0,
>>>> deltaT=900.0,
>>>> abEps=0.1,
>>>> # needed for sea ice
>>>> forcing_In_AB = .FALSE.,
>>>> ChkptFreq=31104000.
>>>> pChkptFreq=311040000.,
>>>> taveFreq=311040000.0,
>>>> dumpFreq=31104000.,
>>>> monitorFreq=2592000.0,
>>>> tauThetaClimRelax=2592000.0,
>>>> dumpInitAndLast=.TRUE.,
>>>> pickupStrictlyMatch=.FALSE.,
>>>> &
>>>> # gridding parameters
>>>> &PARM04
>>>> usingSphericalPolarGrid=.TRUE.,
>>>> delX=0.5,
>>>> delY=100*0.5,
>>>> xgOrigin=0.,
>>>> ygOrigin=-80.,
>>>> delR=10., 10., 10., 10., 10., 10., 10., 12., 14.,
>>>> 16., 19., 22., 26., 30., 36., 42., 50., 60.,
>>>> 72., 85., 100., 120., 140., 166., 200., 200., 200.,
>>>> 200., 200., 200., 200., 200., 200., 200., 200., 200.,
>>>> 200., 200., 200., 200., 200., 200., 200., 200.
>>>> &
>>>> # Input datasets
>>>> &PARM05
>>>> bathyFile='bathyFile_shelf_2Dchan.bin',
>>>> zonalWindFile='zonalWindFile.bin',
>>>> thetaClimFile='thetaClimFile_WOA98_2Dchan.bin',
>>>> diffKrFile='diffKrFile_nosponge_2Dchan.bin',
>>>> hydrogThetaFile='hydrogThetaFile_WOA98_2Dchan.bin',
>>>> hydrogSaltFile='hydrogSaltFile_WOA98_2Dchan.bin',
>>>> &
>>>>
>>>> ########## data.pkg ##############
>>>> &PACKAGES
>>>> useMNC = .TRUE.,
>>>> useGMREDI = .TRUE.,
>>>> useGGL90 = .TRUE.,
>>>> useRBCS = .TRUE.,
>>>> &
>>>>
>>>> ######## data.gmredi ##############
>>>> &GM_PARM01
>>>> GM_MNC = .FALSE,
>>>> GM_AdvForm = .TRUE.,
>>>> GM_UseBVP = .TRUE.,
>>>> GM_background_K = 2000,
>>>> GM_isopycK = 2000,
>>>> GM_Kmin_horiz = 50,
>>>> GM_taper_scheme = 'dm95',
>>>> GM_BVP_ModeNumber = 1,
>>>> GM_BVP_cMin = .1,
>>>> &end
>>>>
>>>> ########### data.ggl90 ############
>>>> &GGL90_PARM01
>>>> GGL90writeState=.FALSE.,
>>>> GGL90TKEmin = 1.e-7,
>>>> mxlMaxFlag=2,
>>>> GGL90mixingLengthMin=3.,
>>>> &
>>>>
>>>>
>>>> ############ SIZE.h ##############
>>>> ...
>>>> PARAMETER (
>>>> & sNx = 1,
>>>> & sNy = 100,
>>>> & OLx = 4,
>>>> & OLy = 4,
>>>> & nSx = 1,
>>>> & nSy = 1,
>>>> & nPx = 1,
>>>> & nPy = 1,
>>>> & Nx = sNx*nSx*nPx,
>>>> & Ny = sNy*nSy*nPy,
>>>> & Nr = 44)
>>>> ...
>>>>
>>>>
>>>> <W.png>_______________________________________________
>>>>
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>>>> MITgcm-support at mitgcm.org <mailto:MITgcm-support at mitgcm.org>
>>>> http://mitgcm.org/mailman/listinfo/mitgcm-support
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>> ---
>> Patrick Heimbach |heimbach at mit.edu <mailto:heimbach at mit.edu> |http://www.mit.edu/~heimbach
>> MIT | EAPS 54-1420 | 77 Massachusetts Ave | Cambridge MA 02139 USA
>> FON+1-617-253-5259 <tel:%2B1-617-253-5259> | FAX+1-617-253-4464 <tel:%2B1-617-253-4464> | SKYPE patrick.heimbach
>>
>>
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--
--
Nicolas Grisouard - Postdoctoral Scholar
Stanford School of Earth Sciences
473 via Ortega - room M11
Stanford, CA 94305-4216
Dept. fax: (+1) 650-498-5099
Office Skype ID: nicolas.grisouard
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