[MITgcm-support] Help me get rid of my noise!
Ryan Abernathey
ryan.abernathey at gmail.com
Thu May 8 12:06:36 EDT 2014
Hi folks,
Thanks to everyone for your feedback. I am going to resurrect this thread,
because I still have some weirdness happening in my mixed layer.
After integrating longer, the stuff over the slope settled down. However,
there are still apparently some strong, shallow convection cells happening
in my mixed layer in the northern part of the domain, just as Jody
suggested. (See new attached figure.) There are little convective chimneys
with the width of a single grid point, so perhaps this is the hydrostatic
convection that Christopher mentioned. These cells lead to lots of grid
scale weirdness at the base of the mixed layer. In particular, there are
sharp grid-scale meridional gradients in the vertical diffusive heat flux
(the step-like patten visible in the third panel), accompanied by strange
looking patterns of GGL TKE. These cells are completely steady and
persistent in time. (The GMREDI parametrization is not the culprit--its
fields are relatively smooth. And almost the exact same thing happens with
KPP instead of GGL.)
I just don't understand why I should be having resolved "convection"
happening in my mixed layer. Isn't the job of the boundary layer
parameterization? This is problematic for me because the meridional heat
transport associated with these mixed layer cells results in the surface
heat flux being unevenly communicated to the interior. For my particular
application, I would really prefer for these fields to be more smooth.
So is this also physically realistic? My feeling is no. And if not, how can
I eliminate them!?
Thanks again.
-Ryan
On Wed, May 7, 2014 at 6:02 PM, Jody Klymak <jklymak at uvic.ca> wrote:
> 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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> >>
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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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> >>
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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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> > --
> > --
> > 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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