[MITgcm-support] On the horizontal momentum budget in the MITgcm

Wed Dec 27 11:36:47 EST 2017

Hi Yi Liu,

The equation seems right to me.
Be sure to get the tendency from the vertical viscous flux with the following equation for the kth level:
( VISrI_Um^k+1 - VISrI_Um^k ) / Cell_Vol
For the surface layer, VISrI_Um^1 should be zero.

Best,
Bertrand

De : MITgcm-support <mitgcm-support-bounces at mitgcm.org> au nom de liuyi315 <liuyi315 at mails.ucas.ac.cn>
Répondre à : "mitgcm-support at mitgcm.org" <mitgcm-support at mitgcm.org>
Date : mercredi 27 décembre 2017 à 3:42 PM
À : mitgcm-support <mitgcm-support at mitgcm.org>
Objet : Re: [MITgcm-support] MITgcm-support Digest, Vol 174, Issue 16

Hi, Dr. Bertrand,

Thanks! I have followed up your advice to do the momentum balance, and the equation is as follows:
TOTUTEND/86400=-g*d(Eta)/dx+Um_Diss+Um_Advec+Um_dPHdx+Um_Ext+AB_gU+VISrI_Um/volume
note that, (1) I did not use CD scheme (2) I used implicit vertical viscosity (3) I took into account the AB effect..
Unfortunately, the equation still could not balance... I chose snapshot (not time-averaged) outputs, and selected the surface layer for the computation. I am very confused about it and do not know where is wrong.
Any suggestions is welcome! Thanks again.

Best,
Yi Liu
On 12/26/2017 23:28，<mitgcm-support-request at mitgcm.org><mailto:mitgcm-support-request at mitgcm.org> wrote：
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Today's Topics:

   1. Re: [mitgcm-support] On the horizontal momentum budget in the
      MITgcm (Bertrand Louis Rene Delorme)
   2. Re: Zeroing quantities in the bottom (Jean-Michel Campin)
   3. flow over 3d Gaussian topography (subhajit kar)

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Message: 1
Date: Tue, 26 Dec 2017 09:46:15 +0000
From: Bertrand Louis Rene Delorme <bdelorme at stanford.edu>
To: "mitgcm-support at mitgcm.org" <mitgcm-support at mitgcm.org>
Subject: Re: [MITgcm-support] [mitgcm-support] On the horizontal
  momentum budget in the MITgcm
Message-ID: <BEB4D437-A4BC-4813-81F8-E2A237F83526 at stanford.edu>
Content-Type: text/plain; charset="utf-8"

Hi Yi Liu,

Not sure that it will help but here are a few points to check:

-          If you don?t use the CD-Scheme, then Um_Advec already contains the Coriolis term.

-          If you use implicit vertical viscosity, that needs to be added (using the flux diagnostic VISrI_Um).

-          The AB effect ? who should be small - should be added with the diagnostic AB_gU.

Best,
Bertrand

De : MITgcm-support <mitgcm-support-bounces at mitgcm.org> au nom de liuyi315 <liuyi315 at mails.ucas.ac.cn>
R?pondre ? : "mitgcm-support at mitgcm.org" <mitgcm-support at mitgcm.org>
Date : lundi 25 d?cembre 2017 ? 1:54 PM
? : mitgcm-support <mitgcm-support at mitgcm.org>
Objet : [MITgcm-support] [mitgcm-support] On the horizontal momentum budget in the MITgcm

Dear all,

Now I am using MITgcm to study the effects of tidal mixing in the Indonesian Seas. I have encountered a problem. I am trying to do the momentum budget analysis using the following equation:
?TOTUTEND/86400=-g*d Eta/dx+Um_Diss+Um_Advec+Um_Cori+Um_dPHdx+Um_Ext"
However, the left term could not balance the right and the difference between them is very large. I am not sure whether I have mistakenly ignored some terms or not.
Could anyone give me some suggestions? Thanks very much.

Best,
Yi Liu
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Message: 2
Date: Tue, 26 Dec 2017 08:39:53 -0500
From: Jean-Michel Campin <jmc at mit.edu>
To: mitgcm-support at mitgcm.org
Subject: Re: [MITgcm-support] Zeroing quantities in the bottom
Message-ID: <20171226133953.GA26957 at ocean.mit.edu>
Content-Type: text/plain; charset=iso-8859-1

Hi Rahele,

Did you check that the model bottom level (k=Nr) is not empty ?
This can easily be done by looking at the last level (k=Nr) of grid file
variables hFacC, hFacW or hFacS : if all zero, then it means that there
is no water there and therefore T,S,U,V would also be zero.

Cheers,
Jean-Michel

On Tue, Dec 19, 2017 at 10:01:15PM +0000, rahele shafiee wrote:
>
> Hi everyone
>
> I have modeled the northern india region. I have usedpackages ???mnc??? and ???obcs???. When it comes to model outputs at points,temperatures, salinity, U, and V ?reach? reaches zero at?the bottom (seabed)?. Can anyone guide me what I've done wrong
> Thank youRahele

> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support

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Message: 3
Date: Tue, 26 Dec 2017 20:50:10 +0530
From: subhajit kar <subhajitkar19 at gmail.com>
To: mitgcm-support at mitgcm.org
Subject: [MITgcm-support] flow over 3d Gaussian topography
Message-ID:
  <CABUV2NiZMAD0DDxnJ4UM2hn6WTjMyC1FinhKOd2QoN9Ua6ZQmg at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Hi all,

   I am trying model a flow over a Gaussian topography using exp4 example.

   I should a surface imprint of topography on the free surface according
to hydraulic theory.

   I am getting something which is not exactly surface imprint. I have
attached a snapshot of surface elevation due to topography.

   Also the boundary has a zero surface height value.

   Is there any way I can give a periodic boundary condition?

Thanks,
Subhajit
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