[MITgcm-support] MITgcm-support Digest, Vol 244, Issue 6

赖燕红 yhlai at pku.edu.cn
Tue Oct 17 02:37:46 EDT 2023


Hi Martin,
Thank you very much for your helpful suggestions!
The asymmetry in my results has been removed after I average the theta before the criterion according to your advice.

Yanhong

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> 发送时间: 2023-10-17 00:00:07 (星期二)
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> 主题: MITgcm-support Digest, Vol 244, Issue 6
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> Today's Topics:
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>    1. Re: Asymmetric surface temperature under symmetric forcing
>       when rbcs package is used (Martin Losch)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Mon, 16 Oct 2023 17:41:57 +0200
> From: Martin Losch <Martin.Losch at awi.de>
> To: MITgcm Support <mitgcm-support at mitgcm.org>
> Subject: Re: [MITgcm-support] Asymmetric surface temperature under
> 	symmetric forcing when rbcs package is used
> Message-ID: <AD5B8961-4568-45D3-8D6F-A41ADE78C8AA at awi.de>
> Content-Type: text/plain; charset="utf-8"
> 
> Just a guess:
> 
> The MITgcm uses a C-grid, so that the velocities are staggered, i.e. the vVel-points are 1/2 grid cell ?south? of the theta points. If you want to preserve symmetry, you could try to average the theat first to velocity points before evaluating your criterion, e.g.
> 
>         IF (0.5*(theta(i,j,k,bi,bj)+theta(i,j-1,k,bi,bj)) .LE. 1700.) THEN
>           gTendency(i,j) = gTendency(i,j)
>      &       - RBC_maskV(i,j,k,bi,bj)*rec_tauRlx
>      &        *( vVel(i,j,k,bi,bj)- RBCvVel(i,j,k,bi,bj) )
>         ENDIF
> 
> Martin
> 
> > On 16. Oct 2023, at 08:05, ??? <yhlai at pku.edu.cn> wrote:
> > 
> > Hello everyone! 
> > 
> > I'm trying to simulate the ocean circulation under a zonally-symmetric surface temperature forcing in a 2D domain (x-z). 
> > Surface temperature is relaxed to a prescribed distribution with a timescale of 20000 s, and Ts ranges from 50 K at the east/west boundaries (?120?) to 3000 K at the substellar point (0?). 
> > But not sure why, the snapshot temperature and other fields (u, SSH, w) always show asymmetric pattern around the substellar point (Figure 1 attached). 
> > I checked the codes and results, and find that the asymmetric results occur after the rbcs package is included and a condition is added in the rbcs_add_tendency.F,this condition is added to reduce the velocity to zero when T<1700 K. 
> >       IF ( tracerNum.EQ.-2 .AND. useRBCvVel ) THEN
> >         rec_tauRlx = rbcsVanishingFac/tauRelaxV
> >         DO j=0,sNy+1
> >          DO i=0,sNx+1
> >         IF (theta(i,j,k,bi,bj) .LE. 1700) THEN
> >           gTendency(i,j) = gTendency(i,j)
> >      &       - RBC_maskV(i,j,k,bi,bj)*rec_tauRlx
> >      &        *( vVel(i,j,k,bi,bj)- RBCvVel(i,j,k,bi,bj) )
> >         ENDIF
> >          ENDDO
> >         ENDDO
> >       ENDIF
> > And there is no asymmetry when rbcs is Off or rbcs is On and the condition is not included under the same thermal forcing. 
> > 
> > Actually I can't understand the asymmetry in surface temperature, because it should be the same to the prescribed surface forcing, which should not be affected even by the rbcs package? 
> > 
> > Do you know how to solve this problem? Any suggestions are welcomed! 
> > By the way, there are large negative vertical velocity in the west and east boundaries (top right panel; w; Figure 1), I guess it might be induced by numerical problem.If you know the reason please tell me. 
> > Thanks very much in advance! 
> > And the data.rbcs and data files I used are listed as below: 
> > 
> > %%%%%%%%%%%%%%%%%%%% data.rbcs # RBCS package parameters:
> >  &RBCS_PARM01
> >  useRBCuVel=.TRUE.,
> >  useRBCvVel=.TRUE.,
> >  tauRelaxU=4000.,
> >  tauRelaxV=4000.,
> >  relaxMaskUFile='U_relax_mask.bin'
> >  relaxMaskVFile='V_relax_mask.bin'
> >  relaxUFile='U_relax.bin',
> >  relaxVFile='V_relax.bin' 
> > 
> > # Note that U/V_relax_mask = 1.0 everywhere, and U/V_relax = 0.0 everywhere. 
> > 
> > %%%%%%%%%%%%%%%% some codes in data  &PARM01
> >  tRef=43*50.,
> >  sRef= 43*34.7,
> >  cosPower=1.,
> >  viscAr=1.E-3,
> >  viscAh=12.E5,
> >  no_slip_sides=.TRUE.,
> >  no_slip_bottom=.TRUE.,
> >  bottomDragLinear=1.E-3,
> >  diffKhT=1.E3,
> >  diffKrNrT=43*1.E-3,
> >  ivdc_kappa=100.,
> >  implicitDiffusion=.TRUE., 
> >  &PARM04
> >  usingSphericalPolarGrid=.TRUE.,
> >  delRc = 40, 40, 40, 40, 40, 40, 40, 50, 50, 50, 50, 50, 50, 50, 50, 50, 60, 60, 60, 80, 80, 80, 100, 100,
> >     100, 100, 100, 100, 100, 100, 150, 150, 150, 200, 200, 200, 200, 200, 300, 300, 300, 300, 400, 400,
> >  rSphere=9E6,
> >  xgOrigin=-120.,
> >  delY=1*2.5,
> >  delX=96*2.5,
> >  &
> > 
> > # Input datasets
> >  &PARM05
> >  bathyFile='topo_nx96ny1_5km.bin',
> >  thetaClimFile='sst_Tm3000K.bin',
> >  & 
> > 
> > 
> > Best regards, Yanhong  
> > 
> > 
> > <Figure 1.png>_______________________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support
> 
> 
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