[MITgcm-support] Temperature drift in tutorial ( tutorial_global_oce_latlon: Global Ocean Simulation at 4◦ Resolution).

[Krishnakumar Rajagopalan]

Hi Martin,

Thanks a lot for reviewing the writeups. I will continue to check the tutorial 
setups and their writeups and post whenever I find some difference in this and 
other tutorials.

Best regards

Krishnakumar



________________________________
From: Martin Losch <Martin.Losch at awi.de>
To: mitgcm-support at mitgcm.org
Sent: Mon, May 2, 2011 12:55:54 AM
Subject: Re: [MITgcm-support] Temperature drift in tutorial ( 
tutorial_global_oce_latlon: Global Ocean Simulation at 4◦ Resolution).

Hi,

Krishnakumar, thanks for your help!

I have added/removed more text to make this section independent of the old exp2. 
The description is still quite incomplete, but I think it's better to have this 
than to carry on with the clearly wrong description. I left a warning at the 
beginning.

Most of the required figures are already available in the 
tutorial_global_oce_in_p section (except for bathymetry).

Jean-Michel, I couldn't make the build-scheme work with your recent changes, but 
I checked it in anyway hoping that it works or that you can fix it.

Krishnakumar, maybe you can continue based on the the current text and the next 
section (tutorial_global_oce_in_p), if you like.

Martin

On Apr 26, 2011, at 7:55 AM, Krishnakumar Rajagopalan wrote:

> Hi Martin,
>  
> I have made changes to climatalogical_ogcm.tex and inp_data.templ that 
>describe  /tutorial_global_oce_latlon.
> I have also included some figures which  are currently commented in 
>climatalogical_ogcm.tex . The brief_note_changes  describes the main changes. 
>The .gz file contains all these documents. Please take a look. Let me know if I 
>need to change/modify anything.
>  
> Thanks a lot
>  
> Best regards
>  
> Krishnakumar
>  
> 
> From: Martin Losch <Martin.Losch at awi.de>
> To: mitgcm-support at mitgcm.org
> Sent: Mon, April 11, 2011 11:30:18 PM
> Subject: Re: [MITgcm-support] Temperature drift in tutorial ( 
>tutorial_global_oce_latlon: Global Ocean Simulation at 4◦ Resolution).
> 
> Dear Krishnakumar,
> 
> thanks for your suggestions.
> 
> The manual usually lags behind the code development, but I agree that the 
>tutorials should be kind of up-to-date. One way of getting this accomplished is 
>that you contribute by updating the tex source (obtain them via: cvs 
>${youroptions} co manual). You can send you changes (somewhere in 
>s_examples/global_oce_latlon/) to this list, and I'll be happy to check this 
>into the repository. Is diffKhT/S=0 is the only detail requiring and update?
> 
> In general you are allowed to have both gmredi turned on and specify a 
>horizontal diffusion. I agree that it does not make much sense, especially since 
>gmredi has it's own minimal horizontal diffusion, but there might be cases when 
>you want to do this for test purposes. The MITgcm is not a black-box that you 
>can use without applying some of your own experience/training (and I have the 
>feeling that you are doing this right now)
> 
> You cannot expect to get the same results as Danabasoglu (2004), because the 
>forcing is not the same and the model is different (different code/MOM, 
>different grid, different parameters, etc.). On the contrary, I think that the 
>correspondence between your curve and the ones by Danabasoglu is most striking. 
>So everything seems to be in order from my point of view.
> 
> Martin
> 
> On Apr 11, 2011, at 9:11 PM, Krishnakumar Rajagopalan wrote:
> 
> > Hi All,
> > I have an update on the temperature drift in tutorial. 
> > In the write up of the Global Ocean Simulation at 4 deg resolution (in the 
>.pdf manual), 
>
> > the horizontal diffusion coefficient for salt and theta, diffKh  is set at  
>1.E3. 
>
> > But, the tutorial is configured to use the GMREDI package, thus diffKh has to 
>be zero. Note that the \input\data  of this tutorial
> > is correct with diffKh=0 in the input file.
> > I think it would be good if the manual (.pdf document) is  revised. I 
>followed 
>
> > the manual and did many runs with diffKh=1e3 and GMREDI package, only 
>realizing
> > the mistake after reading  the writeup on \tutorial_cfc_offline where it is 
>spelled out that
> > when GMREDI package is used, diffKh must be zero.
> > 
> > I think when we set diffKh to some value, and also use GMREDI package, the 
>diffusive flux,
> > df gets calculated once outside the GMREDI_XTRANSPORT subroutine, before 
>being incremented
> > within GMREDI_XTRANSPORT. A configuration check to tell users to ensure 
>diffKh=0 when
> > using GMREDI scheme would be great.
> >  
> >  The attached figure (a) shows two cases where GMREDI package is used. In 
>case 1, diffkH
> > for salt and theta is set as 1e3. In case 2 diffKh=0. Thus case 2 is the 
>correct setting.
> > The results show that the overshoot of theta is larger in case 1.
> > Danabasoglu (Ocean Modelling 7 (2004); 323-341; Fig1) showed that the mean 
>theta
> > increases to about 4.25 degrees when the tracer and momentum time step are 
>different and stays constant
> > thereafter. However, in my case (case 2), the mean theta is seen to reduce 
>after reacing a maximum of about
> > 4.15 deg. Any ideas on why this is happening is most welcome. ( I am yet to 
>run cases where the
> > tracer and momentum time steps are equal)
> >  
> > 
> > Thanks in advance
> >  
> > Krishnakumar
> > 
> 
> 
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