[MITgcm-support] How to simulate the geostrophic current?

[Klymak Jody]

Hi Paul,

Are you sure you specified the correct velocity?  Remember that if eta =0 then u=0 at the surface as well.

Beyond that, the model *will* spin down if there are no energy sources.  Do you have free-slip or no-slip bottom boundary layers?  If no-slip, it will definitely spin down and, depending on your domain size, quite quickly.  Try running with as little mixing or viscosity as possible, and geostrophic balance should be maintained for quite a while.  

Cheers,   Jody



On 2011-03-18, at 1:32 AM, miaocb wrote:

> Hi Jody,
>   Thank for your comments. I initialized the velocity field by using the geostrophic relationship. But the velocity drifted away from the initial value. And I still can not get the right answer.
> The horizontal resolution is 2000m in my configuration. Please tell me the trick if you work it out. Thanks.
> 
> Paul 
> 
>> From: Klymak Jody <jklymak at uvic.ca>
>> To: mitgcm-support at mitgcm.org
>> Subject: Re: [MITgcm-support] How to simulate the geostrophic current?
>> Message-ID: <BAAF5130-5337-4A9F-8729-122405E0242E at uvic.ca>
>> Content-Type: text/plain; charset=us-ascii
>> 
>> Hi Paul,
>> 
>> Given your reply to Martin, your approach looks good to me, though I've not tried this set up before.   
>> 
>> If I were doing a tidal simulation I would set tauRelaxT quite a bit longer than a tidal period, or you will damp your waves.
>> 
>> You don't seem to specify a uVelInitFile or vVelInitFile under PARM05.  I would do so, otherwise your response will be dominated by geostrophic adjustment for many inertial periods >and will take a long time to spin up to steady state.  You will keep trying to relax to a condition that is *not* geostrophically consistent with your initial conditions.  
>> 
>> Finally, I am not sure what viscAh you should be using, because you don't really specify your horizontal resolution.  But for high-resolution internal tide runs I just use 1e-4, and the >model runs fine.  
>> 
>> Anyway, I expect you didn't initialize the velocity, and that is why your model is behaving funny, and also why a short relaxation timescale seems desirable.  
>> 
>> Hope that is of some help.
>> 
>> Cheers,    Jody
> 
> 
> 
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