[Mitgcm-support] Re: advection schemes

[mitgcm-support at dev.mitgcm.org]

Even if the zonal symmetry is not broken, my setup (checkpoint50a_post) 
is in:

sea:/data/mlosch/chkpt50a/channel

Martin

support at mitgcm.org wrote:
> It sounds like there's a bug in the periodic part of the flux limiters.
> Don't know why or where but thanks for volunteering to find out. :-)
> 
> Can you put the set-up somewhere local at MIT for us to see...
> 
> A.
> 
> 
>>-----Original Message-----
>>From: Martin Losch [mailto:mlosch at awi-bremerhaven.de]
>>Sent: Thursday, May 08, 2003 10:34 AM
>>To: support at mitgcm.org
>>Subject: Re: advection schemes
>>
>>
>>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
>>
>>
> 
> 


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