No subject

> Vb(i,j,k)=KWY(i,j,k+1)*0.5-KWY(i,j,k)*0.5;
and since KWY(:,:,1)=0 (from MITgcm code) and KWY(:,:,16)=0 (as set earlier)
we should always get zero for the stream-function at the bottom,
independently of what is in the file GM_Kwy-T, as long as KWY(:,:,1)=0

Could you double check this part ?

Thanks,
Jean-Michel

On Wed, Jun 12, 2013 at 12:50:08PM +0200, Lars Czeschel wrote:
> Hi Ryan,
> it seems it is not a problem of the layer diagnostic.
> I calculated the eddy-MOC from the bolus velocities in z-levels 
> for the 'tutorial_global_oce_latlon' for year 10 with similar results.
> 
> I attached some figures showing the global eddy MOC for both cases and the differences.
> The last two figures show the eddy MOC in the deepest level to give an impression of the 
> divergence when using the skew flux formulation.
> 
> I also attached the matlab code in case I am missing something in my calculation.  
> 
> Thanks, Lars
> 
> 
> 
> 
> 
> 
> 
> %Eddy MOC from skew flux formulation
> clear all
> % load data
> DXG = rdmds('DXG');
> hFacS = rdmds('hFacS');
> YG = rdmds('YG');
> DRF = rdmds('DRF');
> DRF = squeeze(DRF);
> KWY = rdmds('GM_Kwy-T.0000172800');
> 
> % compute mer. bolus velocity
> KWY(:,:,16)=0.0;
> for i=1:90
> for j=1:40
> for k=1:15
> Vb(i,j,k)=KWY(i,j,k+1)*0.5-KWY(i,j,k)*0.5;
> end
> end
> end
> DX=repmat(DXG,[1,1,15]);
> ddz=repmat(DRF,[1, 40, 90]);
> ddz=permute(ddz,[3 2 1]);
> n=find(hFacS > 0); 
> Vb(n)=Vb(n)./(ddz(n).*hFacS(n));
> 
> % integrate MOC
> Xint=sum(Vb.*DX.*hFacS);
> Xint=squeeze(Xint);
> dz=repmat(DRF,[1,40]);
> dz=permute(dz,[2 1]);
> MOC=cumsum(Xint.*dz./1e6, 2);
> 
> %Plotting
> [hcl cl]=contourf(YG(1,:),cumsum(DRF),MOC',[-30:5:-10 -10:2:10 10:5:30 ]);
> set(gca,'YDIR','reverse')
> clabel(hcl,cl)
> caxis([-30,30])
> colorbar
> title('Skew Flux MOC [Sv]');
> 
> ----
> 
> %Eddy MOC from advective formulation
> clear all
> DXG = rdmds('DXG');
> hFacS = rdmds('hFacS');
> YG = rdmds('YG');
> DRF = rdmds('DRF');
> DRF = squeeze(DRF);
> PSIY = rdmds('GM_PsiYtave.0000172800');
> 
> % compute mer. bolus velocity
> PSIY(:,:,16)=0.0;
> for i=1:90
> for j=1:40
> for k=1:15
> Vb(i,j,k)=PSIY(i,j,k+1)-PSIY(i,j,k);
> end
> end
> end
> DX=repmat(DXG,[1,1,15]);
> ddz=repmat(DRF,[1, 40, 90]);
> ddz=permute(ddz,[3 2 1]);
> n=find(hFacS > 0);
> Vb(n)=Vb(n)./(ddz(n).*hFacS(n));
> 
> % compute eddy MOC
> Xint=sum(Vb.*DX.*hFacS);
> Xint=squeeze(Xint);
> dz=repmat(DRF,[1,40]);
> dz=permute(dz,[2 1]);
> MOC=cumsum(Xint.*dz./1e6, 2);
> 
> %Plotting
> [hcl cl]=contourf(YG(1,:),cumsum(DRF),MOC',[-30:5:-10 -10:2:10 10:5:30 ]);
> set(gca,'YDIR','reverse')
> clabel(hcl,cl)
> caxis([-30,30])
> colorbar
> title('Advective form MOC [Sv]');
> 
> 
> 
> 
> On 06.06.2013, at 18:04, Ryan Abernathey wrote:
> 
> > Lars,
> > Unfortunately, I can't really comment on climatological differences between the skew flux vs adv form.
> > But I am curious whether using adv form fixed the problems you were having with the layers diagnostics.
> > -Ryan
> > 
> 
> > 
> > On Thu, Jun 6, 2013 at 2:24 AM, Lars Czeschel <lars.czeschel at zmaw.de> wrote:
> > Hi all,
> > 
> > i am running a 1deg global model with version MITgcm_63q. Using the layers pkg I noticed
> > that my global overturning in density space is divergent (up to 5 Sv in ACC latitudes).
> > Without bolus velocities or using  ' GM_AdvForm    = .TRUE.,' in data.gmredi
> > the overturning becomes non-divergent.
> > 
> > As we used the skew flux version frequently in the past (which is also the default) I hoped to find
> > a bug in the layers pkg but without success. As a further test I ran the tutorial example
> > 'tutorial_global_oce_latlon'  for 10 years with   GM_AdvForm    = .False. compared
> > to GM_AdvForm    = .TRUE. in data.gmredi. I attached the quite strong differences in theta (z=85m)
> > below.
> > 
> > To my understanding the differences should be very small even if the small slope assumption
> > is made using the skew flux version.
> > 
> > Did I miss something here or do we have an undiscovered bug in the skew flux code and
> > the advective form should be recommended ?
> > 
> >   Thanks , Lars
> > 
> > p.s: Several years ago Christopher Wolfe reported a related problem
> > http://mitgcm.org/pipermail/mitgcm-support/2008-January/005180.html
> > 
> > 
> > ----------------------------------------------
> > Lars Czeschel
> > Theoretical Oceanography
> > Institut für Meereskunde
> > KlimaCampus Universität Hamburg
> > Bundesstr. 53
> > 20146 Hamburg
> > 
> > 
> > _______________________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
> > 
> > 
> > _______________________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
> 

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