[Mitgcm-support] Re: advection schemes

[mitgcm-support at dev.mitgcm.org]

I have to take back, what I said about the zonal symmetry. All runs, 
that started from zonal symmetry, stay symmetric. Thanks God, and please 
excuse my making such an alarm.

But there still this vertical mixing going on accompanied with a rapid 
increase of mean kinetic energy, which I cannot explain. My vertical 
t-gradient of 17K/5000m reduces to 4K/5000m after only 1month of 
integration (2160 timesteps, deltaT=1200sec).

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
>>
>>
> 
>