[Mitgcm-support] Re: advection schemes

[mitgcm-support at dev.mitgcm.org]

Alistair,

my set-up is still in the toy-phase, so I have 20x20x10 points with 
25kmx25kmx500m. My initial stratification is such (similar to Wardle and 
Marshall N/f=21) that the Rossby radius is ~100km. After this initial 
mixing event, this Radius has decreased to 50km and smaller, that is, I 
don't really resolve it anymore. So it's no longer high resolution. But 
shouldn't a zonally symmetric flow stay zonally symmetric forever, 
regardless of the resolution?

Martin

support at mitgcm.org wrote:
> The answer is it shouldn't happen so something is wrong.
> 
> Hope that helps!  :-)
> 
> Is this very high res.?
> 
> A.
> 
> 
>>-----Original Message-----
>>From: Martin Losch [mailto:mlosch at awi-bremerhaven.de]
>>Sent: Thursday, May 08, 2003 8:37 AM
>>To: support at mitgcm.org
>>Subject: advection schemes
>>
>>
>>Hi again,
>>
>>this time I have a question about advection schemes:
>>I have replaced the default advection (2nd order, centered)
>>by the DST-3 
>>with flux limiter (temp/salt/tracerAdvScheme=33, by the way, not very 
>>well documented which idenifying number belongs to which 
>>scheme). In my 
>>channel, I start from a zonally homogeneous (symmetric) state, with a 
>>strong vertical stratification (similar to Wardle and 
>>Marshall, 2000, JPO).
>>
>>I expect (and this is true for the 2nd centered scheme) that,
>>starting 
>>from rest, I spinup my channel ad infinitum, until the CFL 
>>criterium is 
>>violated the model explodes.
>>
>>With the DST-3 with flux limiter, this is NOT what happens,
>>instead the 
>>whole system becomes unstable almost immediately (even if I have some 
>>explicity bi-harmonic friction), I get deep mixing until the 
>>channel is 
>>basically homogenized and then slowly the flow restratifies 
>>according to 
>>my buoyancy forcing, but the zonal symmetry is broken 
>>forever. Is that 
>>supposed to happen?
>>
>>Martin
>>
>>--
>>Martin Losch
>>Alfred Wegener Institute for Polar and Marine Research
>>Postfach 120161, 27515 Bremerhaven, Germany;
>>Tel./Fax: ++49(0471)4831-1872/1797
>>
>>
> 
> 


-- 
Martin Losch
Alfred Wegener Institute for Polar and Marine Research
Postfach 120161, 27515 Bremerhaven, Germany;
Tel./Fax: ++49(0471)4831-1872/1797