[MITgcm-support] questions

[Martin Losch]

Riema,

the MITgcm is z-coordinate model (that is, layers are approximately  
geopotential surfaces). Theres is no bottom-following sigma  
coordinate. Slopes are represented as a step wise stair case as in  
all z-coordinates models. As you may know this approach leads to  
problems with flow down the slope, when the resolution is poor, that  
is, when you don't resolve the slope properly.

tRef/hydrogThetaFile: please have a look at ini_theta.F, where you  
will see, that theta is first initialized with tRef, then overwritten  
with whatever is in the file that you specify for hydrogThetaFile  
(T.init in your case). If hydrogThetaFile = ' ' (default), tRef is  
the initial profiles (everywhere in your domain).
if EOStype = 'LINEAR', tRef/sRef play a second role: they are the  
reference temperaure/salinity in the linear eos: rho = rho0*(1-talpha* 
(theta-tref) + sbeta*(salt-sref)).

Martin

On 30 Oct 2006, at 07:00, Riema Rachmayani wrote:

> hi all..
>
> Is MITGCM using sigma coordinate?? how to treat if there is slope  
> for vertical grid without sigma coordinate??
>
> what the different between T.init and tref in internal_wave  
> verification??
>
> thx
> rima
>
> ----- Original Message ----
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> request at mitgcm.org>
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> Sent: Friday, October 27, 2006 11:00:06 PM
> Subject: MITgcm-support Digest, Vol 40, Issue 16
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> Today's Topics:
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>    1. KPP and KPP_ghatUseTotalDiffus (David Ferreira)
>    2. Re: KPP and KPP_ghatUseTotalDiffus (Martin Losch)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Thu, 26 Oct 2006 20:40:08 -0400
> From: David Ferreira <dfer at ocean.mit.edu>
> Subject: [MITgcm-support] KPP and KPP_ghatUseTotalDiffus
> To: mitgcm-support <mitgcm-support at mitgcm.org>
> Message-ID: <45415568.9000800 at ocean.mit.edu>
> Content-Type: text/plain; charset=us-ascii; format=flowed
>
> Hi,
>
> I just run into the "KPP_ghatUseTotalDiffus" flag in KPP.
> It seems to be adding some contribution coming from
> GM Redi to the KPP diffusivity, but it's not quite to clear to me.
>
> Could someone explain me what this flag exactly does
> and what's the reason for it ?
> Thanks,
> david
>
>
>
> -- 
>
> Ferreira David               Tel : 617 253 7967
> EAPS Room 54-1515,
> Massachusetts Institute of Technology,
> 77 Massachusetts Avenue
> Cambridge, MA, 02139
>
>
>
> ------------------------------
>
> Message: 2
> Date: Fri, 27 Oct 2006 08:38:26 +0200
> From: Martin Losch <mlosch at awi-bremerhaven.de>
> Subject: Re: [MITgcm-support] KPP and KPP_ghatUseTotalDiffus
> To: mitgcm-support at mitgcm.org
> Message-ID: <BA52AD18-38D9-4876-BB03-C92FDADC5F42 at awi-bremerhaven.de>
> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
>
> Hi David,
> as far as I can see, the flag is used in kpp_transport_t/s/ptr where
> the counter-gradient flux (or non-local term) of KPP is applied (the
> second term in the following expression):
> kappa1*dtracer/dz - kappa2*ghat*surfaceFlux
>
> In pure KPP kappa1=kappa2, but GM has a vertical component of kappa
> as well and I guess here you can decide whether this contribution is
> included in kappa2 (it's part of kappa1) as well. I don't know the
> reason/"physics" behind this.
>
> Martin
>
> On 27 Oct 2006, at 02:40, David Ferreira wrote:
>
> > Hi,
> >
> > I just run into the "KPP_ghatUseTotalDiffus" flag in KPP.
> > It seems to be adding some contribution coming from
> > GM Redi to the KPP diffusivity, but it's not quite to clear to me.
> >
> > Could someone explain me what this flag exactly does
> > and what's the reason for it ?
> > Thanks,
> > david
> >
> >
> >
> > --
> >
> > Ferreira David               Tel : 617 253 7967 EAPS Room 54-1515,
> > Massachusetts Institute of Technology,
> > 77 Massachusetts Avenue
> > Cambridge, MA, 02139
> >
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> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
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>
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