[MITgcm-support] Momentum Budget

[Jean-Michel Campin]

Hi Christopher,

Just 2 remarks:
1) if your forcing includes Atmospheric pressure loading (=atmP_load), 
 this contribution (= -gradient) needs to be added:
    -1/rhoConst * ( atmP_load(i) - atmP_load(i-1) ) / DXC
 and the same thing applies to seaice-loading:
    -gravity/rhoConst * ( sIceLoad(i) - sIceLoad(i-1) ) / DXC

 note that the fixed density to use is "rhoConst" and not "rhoConstFresh"

2) I think that at this level of the momentum budget decomposition,
 it should be valid for both the Flux-Form formulation and 
 for the Vector-invariant formulation.

Cheers,
Jean-Michel

On Mon, Feb 10, 2014 at 01:31:04PM -0500, Christopher Piecuch wrote:
> All,
> 
> There have been some emails going around over the past couple of
> months (and years) regarding closure of momentum budgets using
> MITgcm. I have another question on this topic, if anyone still has
> energy for this issue.
> 
> I am trying to close offline the momentum budgets on an LLC grid
> using the general setup for the upcoming ECCO-Production (Version 4)
> release. I am diagnosing the budget using 64-bit output following
> methods spelled out in Jean-Michel's most recent post on this issue (http://mitgcm.org/pipermail/mitgcm-support/2013-December/008719.html)
> as
> 
> TOTUTEND/86400 = -gravity*d(SSH)/dx + Um_dPHdx + Um_Advec + Um_Diss
> + Um_Ext + AB_gU + Implicit Vertical Diffusion,
> 
> where SSH = ETAN + sIceLoad/rhoConstFresh and I'm computing the
> horizontal gradients in the SSH using Gael Forget's gcmfaces
> package.
> 
> I'm finding that the correspondence between right-hand and left-hand
> sides of the above equation seems to degrade with depth and
> proximity to sea-ice.
> 
> Since the setup I am considering uses the vector-invariant momentum
> equations (vectorInvariantMomentum=.TRUE.), and not the flux-form
> version that seems to be the topic of all previous threads, I am
> wondering: are there additional terms that need to be output to
> diagnose the momentum budgets for the vector-invariant case?
> 
> If not, it is probably the case I have some bugs in my post-processing code.
> 
> Any input would be appreciated. Please let me know any setup files,
> etc., that might be needed to help diagnose the issue.
> 
> Thanks very much in advance,
> Chris
> 
> -- 
> Christopher G. Piecuch, Staff Scientist
> Atmospheric and Environmental Research (AER), a Verisk Analytics company
> 131 Hartwell Avenue, Lexington, MA 02421 USA
> p: +1.781.761.2349 | email: cpiecuch at aer.com | www.aer.com
> 
> 
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