[MITgcm-support] Help me get rid of my noise!
Jody Klymak
jklymak at uvic.ca
Wed May 7 18:02:36 EDT 2014
Hi guys,
Its not just shallower (and weaker) convection in the mixed layer?
Cheers, Jody
On May 7, 2014, at 14:52 PM, Nicolas Grisouard <nicolas.grisouard at stanford.edu> wrote:
> Hi,
>
> We must be talking about something different. The isopycnal slope I was referring to (weren't you?) is in the mixed layer, outcropping near y = -60 and dropping by 500 m within one horizontal grid cell: 50 km? If yes, that's a 1% slope, which is actually fairly steep. And it looks like it could be more, resolution permitting.
>
> But if the PV is negative everywhere, I stand corrected.
>
> Cheers,
> Nico.
>
> On Wed 07 May 2014 02:27:34 PM PDT, Ryan Abernathey wrote:
>> 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
>> <mailto: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>
>> <mailto: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>>
>> <mailto: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>>
>> <mailto: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>>
>> <mailto: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>>
>> <mailto: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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>> ---
>> Patrick Heimbach |heimbach at mit.edu
>> <mailto:heimbach at mit.edu> <mailto:heimbach at mit.edu
>> <mailto:heimbach at mit.edu>> |http://www.mit.edu/~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 <tel:%28%2B1%29%20650-498-5099>
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> --
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> 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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