[MITgcm-support] questions about non-hydrostiatic module

宋 朋洋 peterspy at outlook.com
Fri Sep 22 16:54:42 EDT 2017

Thanks for your reply, Jean-Michel.

1.     Sorry, I didn’t understand what you mean by “Delta t”. I think that u** and v** is a correction of u* and v* by surface elevation, which still has a dimention of velocity (m/s) , but what is needed on the right side of Eq.(2.68) is a dimention of acceleration (m/s^2). Did you mean \partial_t?

2.     I think to MITgcm, it is more safe to calulate by continuity, because nonhydrostatic pressure is solved by a method of iteration, errors can always exist. However, continuity is a strong constraint to stability, compared to forward integration. Just personal idea.
Pengyang Song

发件人: mitgcm-support-request at mitgcm.org<mailto:mitgcm-support-request at mitgcm.org>
发送时间: 2017年9月23日 0:00
收件人: mitgcm-support at mitgcm.org<mailto:mitgcm-support at mitgcm.org>
主题: MITgcm-support Digest, Vol 171, Issue 9

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Today's Topics:

   1. Re: questions about non-hydrostiatic module (Jean-Michel Campin)


Message: 1
Date: Thu, 21 Sep 2017 18:50:03 -0400
From: Jean-Michel Campin <jmc at mit.edu>
To: mitgcm-support at mitgcm.org
Subject: Re: [MITgcm-support] questions about non-hydrostiatic module
Message-ID: <20170921225003.GA6558 at ocean.mit.edu>
Content-Type: text/plain; charset=iso-8859-1

Hi Pengyang,

Regarding question 1, I think a "Delta t" is missing there.
Thanks for pointing to this.
But probably better to keep u**, v** & w** (not wrong) to remain
closer to what is done in the code.

And regarding question 2, the fluid is incompressible, so the
continuity equation has to be satisfied as well as the prognostic equation for w(n+1).
In the analytical form, the system of equations guarantees both.
And indeed, when/if the solver converges perfectly, the two equations
give the same answer.


On Thu, Sep 21, 2017 at 07:45:58AM +0000, ??? ?????? wrote:
> Hi all,
> I am reading the manual of MITgcm about non-hydrostatic part. Here are
> some questions:
> http://mitgcm.org/public/r2_manual/latest/online_documents/node39.html
> 1.? In equation 2.68, is it written by mistake at the right side? By
> Marshall et al.(1997), it should be Gu, Gv, Gw instead of u**, v**, w**.
> 2.? In equation 2.71, in non-hydrostatic scheme, w should be prognostic
> instead of diagnostic, should it be something like w(n+1)=w(*)+dt * (
> \partial_z p_nh ) ?
> Regards,
> Pengyang Song
> Ocean University of China
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support


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