[MITgcm-support] is it feasible to use tRef, sRef as initial conditions

[Dimitris Menemenlis]

Typically when we initialize model from a climatology, we have to use
much shorter time step initially, e.g., first day or so, to reduce CFL shocks.
As you ruhn the model check the "advcfl" diagnostics in the STDOUT
files and make sure they remain below about 0.5.  Then you can gradually
increase time step.  The CFL violation often occurs not because the
initial fields are not sufficiently smooth in the horizontal, but rather because
there are vertical instabilities in these fields, i.e., dense water over light water.

On Feb 26, 2014, at 9:15 AM, 李志远 <oceanlizy at 163.com> wrote:

> From: Li zhiyuan <oceanlizy at 163.com>
> To: MITgcm <mitgcm-support at mitgcm.org>
> Subject:"is it feasible to use tRef,sRef  as initial conditions "
> my dear MITgcm users:
>       There had been a question troubled me for a long time . I used mitgcm to simulate a wind_diriven circulation in an semi-enclosed domain ,such as " N24-N41,E117-E132" . When I use a pre-processed initial temperature and salt input file  (such as Levitus 01 datas) ,the model run some steps then occured "Nan" in the STDOUT file ,but when I use
>  " tRef= 26.5, 25.5, 24.4, 23.1, 21.9,
>        20.5, 18.7, 16.4, 13.6, 11.3,
>        8.9,  6.5,  4.6,  4.6,  4.6,
>        4.6,  4.6,  4.6,  4.6,  4.6,
>        4.6,  4.6,  4.6,  4.6,  4.6,
>        4.6,  4.6,  4.6,  4.6,  4.6,
>        4.6,  4.6,  4.6,  4.6,  4.6,
>       4.6,
>  sRef= 33.28, 33.59, 33.87, 34.13, 34.36,
>        34.53, 34.61, 34.64, 34.56, 34.48,
>        34.39, 34.35, 34.38, 34.38, 34.38,
>        34.38, 34.38, 34.38, 34.38, 34.38,
>        34.38, 34.38, 34.38, 34.38, 34.38,
>        34.38, 34.38, 34.38, 34.38, 34.38,
>        34.38, 34.38, 34.38, 34.38, 34.38,
>       34.38,
>  the model run without errors . I have learnd that  this maybe a CFL problem , because  the initial conditions are not  smooth enough  . But I have smooth the data for many times , I think it is smooth. But things went wrong !!! I do not know  how to make the initial conditions "enough smooth" . 
> So ,I doubt that  is it feasible for me to just use  the above " tRef ,sRef " as a initial conditions .  I want to force the model with wind force,  surface heatflux and salt flux  for few years until the model run steadily ,when I can get a steady state  " temperature , salt filed ", and 
> the" u,v velocity filed" . I guess if feasible , it will take  a much longer time to get such a steady state .  Am  I  right ?
> 
>  Any  quick reply will be great appreciated !
> Yours  Li zhiyuan
> Best regards  ! 

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