[MITgcm-support] Help me get rid of my noise!

Ryan Abernathey ryan.abernathey at gmail.com
Wed May 7 17:27:34 EDT 2014


Nico,

Interesting suggestion, but I don't think that's what's going on. Keep in
mind that the aspect ratio is tiny for this domain. That "steep" isopycnal
still extends over ~2000 km in the horizontal. The slope is ~0.002.
Relative vorticity is completely negligible here, and the PV is everywhere
negative.

-Ryan


On Wed, May 7, 2014 at 4:51 PM, Nicolas Grisouard <
nicolas.grisouard at stanford.edu> wrote:

> 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@
>>> 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@
>>>> 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@
>>>> 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@
>>>>> 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>_______________________________________________
>>>>>
>>>>>     MITgcm-support mailing list
>>>>>     MITgcm-support at mitgcm.org  <mailto:MITgcm-support at mitgcm.org>
>>>>>     http://mitgcm.org/mailman/listinfo/mitgcm-support
>>>>>
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>>>>
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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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>>
>>
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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
> http://nicolas.grisouard.free.fr
> http://www.mendeley.com/profiles/nicolas-grisouard/
>
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