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Hi Jean-Michel,</div>
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No problem at all about the delay and thanks for clarifying this!</div>
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Cheers,</div>
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Flynn</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> MITgcm-support <mitgcm-support-bounces@mitgcm.org> on behalf of Jean-Michel Campin <jmc@mit.edu><br>
<b>Sent:</b> 31 August 2025 9:02 PM<br>
<b>To:</b> mitgcm-support@mitgcm.org <mitgcm-support@mitgcm.org><br>
<b>Subject:</b> Re: [MITgcm-support] GM_Psi diagnostic when using HFacC and DeepFacC- quick question</font>
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<div class="PlainText">Hi Flynn,<br>
<br>
Sorry for answering late, I was away when you posted this message and missed it<br>
afterward.<br>
<br>
To compute the bolus MOC ( MOC(j,k) at latitude yG(:,j), depth rF(k) ) which involves<br>
the double sum over longitude width and from bottom to rF(k) of <br>
vVeli(i,j,k) * dxG(i,j)*deepFacC(k) * drF(k) * hFacS(i,j,k)<br>
and using the model diagnostic GM_PsiY, I don't need the hFacS since GM_PsiY is already<br>
vertically integrated from the bottom. But when I integrate along the longitudinal<br>
direction I need to multiply dxG by deepFacF(k), to get: <br>
<br>
MOC_bolus(j,k) = Sum_(i1,i2){ GM_PsiY(i,j,k) *dxG(i,j)*deepFacF(k) }<br>
<br>
Regarding the deep-geometry factor, there might be other ways to define GM_Psi,<br>
but the expression above is consistent with how it's defined in MITgcm (and match<br>
the code in gmredi_residual_flow.F, lines 61-98).<br>
<br>
Cheers,<br>
Jean-Michel<br>
<br>
On Thu, Aug 07, 2025 at 04:23:58PM +0000, Flynn Ames wrote:<br>
> Dear MITgcm people,<br>
> <br>
> Hello - I'm modelling an ocean using GMREDI with deep atmosphere mode turned on, and topography in the domain.<br>
> I use the GM_Psi diagnostic to compute the bolus meridional overturning streamfunction.<br>
> <br>
> I'm wondering if I should be weighting GM_Psi for HFacC and DeepFacC when computing the bolus volume transport in my offline calculations, or whether the GM_Psi diagnostic has already been weighted by these factors so that this step isn't necessary?<br>
> <br>
> I had previously been doing this, but came across a section in the reentrant channel tutorial stating that weighting the GM_Psi diagnostics for HFacC isn't necessary (I haven't found any info about whether the same holds for deepFacC).<br>
> To sanity check, I'm wondering if someone could confirm the correct approach here?<br>
> <br>
> Thanks in advance!<br>
> Flynn<br>
> <br>
> <br>
<br>
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