[MITgcm-support] Spinup in a 2-D channel surface waves?

[Jody Klymak]

Hi Dmitri,

Yes, the first and last depths in X are zero.

I should mention that I have only one grid point in y.  Is that OK,  
or could it cause the surface algorithm to have difficulties?

Thanks,  Jody

On Oct 5, 2006, at 1:56 PM, Dmitri Leonov wrote:

> Does your topography go all the way to the surface? (Otherwise your  
> channel will be periodic in the cross-channel direction).
> That's the only hint I can think of right now.
>
> Dmitri
>
> Jody Klymak wrote:
>>
>> Hello,
>>
>> I want to perform spinup of a 2-D channel to along-channel winds  
>> for a class I'm teaching.  While I'm sure the MITgcm is overkill  
>> for this, I'm at least vaguely familiar with it.
>>
>> I have the winds blowing, the channel seems to behave, and an  
>> Ekman layer seems to form.  However, the surface pressure is not  
>> behaving and I'm finding the docs on the surface pressure solver  
>> opaque enough that I thought I'd ask for help here.
>>
>> My vertical resolution near the surface is 0.75m, for 40 bins.   
>> The total water depth is as deep as 200 m, with sloping sides in a  
>> 20 km-wide channel.  dx = 200 m.
>>
>> What happens is I blow a south wind, the Ekman layers pile water  
>> up in the west and move it away from the East. However, the depth  
>> anomalies do not seem to get large enough, and the ones that do form
>> do not propagate more than a couple of grid cells away at anything  
>> like the surface wave speed.  For instance, the cross-channel  
>> Ekman flux reaches 1 m^2/s, which should be changing the surface  
>> tilt by something like 36 cm over an hour. However, after 7 h or  
>> so (in sim time), I still have 10 cm-high anomalies in the grids  
>> adjacent to the edge of the channel, and nothing more than 3 grid  
>> cells away.
>>
>> Any hints what I've done wrong or suggestions for getting the  
>> barotropic pressure gradient to set up properly across the channel  
>> would be very helpful!
>>
>> Thanks a lot,  Jody
>>
>> In "data" I hope the relevant parameters are:
>>
>> viscAz=1.E-3,
>> viscAh=1.E-3,
>> no_slip_sides=.FALSE.,
>> no_slip_bottom=.TRUE.,
>> viscA4=0.E12,
>>
>> gBaro=9.81,
>> rigidLid=.FALSE.,
>> implicitFreeSurface=.TRUE.,
>>
>> nonHydrostatic=.FALSE.,
>> hFacMin=0.5,
>> implicSurfPress=0.5,
>> implicDiv2DFlow=0.5,
>> nonlinFreeSurf=3,
>> hFacInf=0.1,
>> hFacSup=2.0,
>> exactConserv=.TRUE.,
>>
>>
>>
>>
>> -- 
>> Jody Klymak
>> http://web.uvic.ca/~jklymak/
>>
>>
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>
>
> -- 
> ------------------------------------------------
> Dmitri A. Leonov
> Research Associate, Postdoctoral
> University of Washington, School of Oceanography
>
>
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--
Jody Klymak
http://web.uvic.ca/~jklymak/