[MITgcm-support] Momentum Budget

[Matthew Mazloff]

Hi Emily,

I believe there are a few tricks to this

Disclaimer -- this info may be out of date or not apply to your  
specific setup....


I think the tendency term is in units per day, not per second, so try  
rescaling from m/s/d to m/s^2 by dividing by 86400

For vector invariant momentum formulation (not sure about flux form)  
Um_Advec includes coriolis

I believe Um_dPHdx does not include pressure forcing from SSH  
gradient, you need to add that in

Note that UBotDrag and USidDrag should be in Um_Diss

If you want to look at the implicit vertical viscous flux (VISrE_Um)  
then I believe this has units m^3/s^2 and so needs to be rescaled by  
surface area ( divide by RAW and RAS for zonal, meridionaly momentum  
balance respectively)


Hope this helps -- or at least gives you some ideas...

-Matt



Request to developers...maybe the momentum diagnostics could be  
cleaned up?




On Dec 7, 2010, at 1:46 PM, Emily Shroyer wrote:

> I would like to output terms of the momentum budget using the  
> diagnostic
> package. My data.diagnostic file is set as:
>
> &diagnostics_list
>  diag_mnc     = .TRUE.,
>  frequency(1) = -43200.,
>  filename(1) = 'UmomDiag',
>  fields(1,1) = 'TOTUTEND','UBotDrag ','USidDrag
> ','Um_Diss','Um_Advec','Um_Cori',
>                'Um_dPHdx','Um_Ext','Um_AdvZ3','UDIAG1  ',
>
>  frequency(2) = -43200.,
>  filename(2) = 'VmomDiag',
>  fields(1,2) = 'TOTVTEND','VBotDrag ','VSidDrag
> ','Vm_Diss','Vm_Advec','Vm_Cori',
>                'Vm_dPHdy','Vm_Ext','Vm_AdvZ3','UDIAG2  ',
>
> &
>
> The terms Udiag1/2 were added to account for gradients in the sea
> surface height. Unfortunately, the total tendency is not quite equal  
> to
> the sum of the other terms. I think that difference may be associated
> with the implicit diffusivity term? I am using a KPP mixing scheme,
> although I have also tried a MY scheme. I spent  a bit of time  
> trying to
> decide where best to output this term with a user defined diagnostic
> without any result. My questions are 1) Is it likely that this is  
> indeed
> the term I am missing in the momentum budget or have a missed  
> something
> else? 3) If so, does anyone have a suggestion as to where best to  
> output
> this term with the user diagnostic?
>
> Thanks for any advice, Emily
>
> -- 
> Emily Shroyer, Postdoctoral Scholar
>
> Woods Hole Oceanographic Institution
> Clark 316A, MS #21
> Woods Hole, MA 02543
>
> phone: 508 289 2525
>
>
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> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
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