[Mitgcm-support] Re: advection schemes

[mitgcm-support at dev.mitgcm.org]

Olx/y=3 (I use KPP as well, but these things happen without KPP as well).

It does not happen with Scheme=3 (3rd order up-wind?) nor 4 (4th order 
centered)
So far it happens only with Scheme=33 and 77.

I also use multiDimAdvection=.true.

Martin

support at mitgcm.org wrote:
> What is Olx,Oly set to? Does this happen with schemes=3?
> 
> A.
> 
> 
>>-----Original Message-----
>>From: Martin Losch [mailto:mlosch at awi-bremerhaven.de]
>>Sent: Thursday, May 08, 2003 10:03 AM
>>To: support at mitgcm.org
>>Subject: Re: advection schemes
>>
>>
>>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
>>
>>
> 
> 


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