[Mitgcm-support] RE: advection schemes

[mitgcm-support at dev.mitgcm.org]

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
> 
>