[MITgcm-support] Zonal velocity bands

[Neil Swart]

Hi Chris,
I have the diagnostic output oceTaux (from the run with the zonal  
bands). It looked okay to me:
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I'm not sure I understand your comment on periodicity for the  
forcing. If I were using an observed windstress (which is what I want  
to do) it would not necessarily be periodic over the domain if I  
understand correctly. Perhaps I'm missing something.

More explicitly, in this case I calculated the windstress  almost  
exactly as setup in the gendata.m file for the baroclinic gyre test  
case:

nx=40;
ny=60;

tauMax=0.1;
x=((1:nx)-0.5)/(nx-1); % nx-1 accounts for a solid wall
y=((1:ny)-0.5)/(ny-1); % ny-1 accounts for a solid wall
[X,Y]=ndgrid(x,y);

tau=tauMax*sin(1.2*pi*Y);

Thanks,
Neil


On 26-Mar-10, at 7:47 AM, Chris Hill wrote:

> Neil,
>
>  It does look a bit odd!
>  One question - you have written tau=tauMax*sin(pi*Y). There should be
> a 1/Ly in the sin function too i.e. some length scale
>  over which the wind is periodic - otherwise you will get something  
> weird.
>  Are you writing the winds to a file - if so a plot of them would  
> be good.
>
> Chris
>
> On Thu, Mar 25, 2010 at 8:20 PM, Neil Swart <ncswart at uvic.ca> wrote:
>>
>>> Hi MITgcmer's,
>>>
>>> I am trying to establish a setup derived from the  
>>> tutorial_baroclinic_gyre example - the differences being I have  
>>> 10 vertical levels, and the domain spans 10-70S, 0-40E.
>>>
>>> With a zonal wind-stress from the example - specified as:  
>>> tau=tauMax*sin(pi*Y); I get something that I think is reasonable  
>>> after the first few steps (output is weekly).
>>
>>>
>>>
>>> If I alter the windstress slightly, to: tau=tauMax*sin(1.2*pi*Y);  
>>> a bunch of alternating zonal 'jets' appear. These strike me a  
>>> being unrealistic and the symptom of some problem. They persist,  
>>> and even intensify if I integrate out to a later time.
>>>
>>
>>>
>>>
>>> If I toy around with the wind-field, I can get this behaviour to  
>>> come or go, seemingly depending on how symmetrical the forcing  
>>> is. Can anyone please help me out with what might be going wrong?  
>>> I'm ultimately trying to implement a
>>> zonally homogeneous windstress derived from the Trenberth  
>>> climatology (doing so produces the same problem).
>>>
>>> Thanks for your help!
>>
>>> Neil
>>>
>>> ---------------------------------------------------
>>> Neil Swart
>>>
>>> Climate Modelling Group
>>> School of Earth and Ocean Sciences
>>> University of Victoria
>>> Victoria, BC
>>> Canada
>>>
>>> http://climate.uvic.ca/
>>>
>>>
>>>
>>
>>
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