[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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>>> ---
>>> 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
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