[MITgcm-support] advection of passive AND active tracers

[Martin Losch]

Hi once more,

because I am alwayes 6 hours ahead of you (o:, (and because this 
problem was really burning under my fingernails), I impatiently found 
the problem with turning off the tracer advection:
with temp/saltAdvection=.false. the routine gad_advection where gTracer 
is reset, or equivalently in gad_calc_rhs gTracer is not reset, so that 
gTracer accumulates tracer+deltat*gTracer, which of course make the 
model blow up.

Remedy:
In thermodynamics one could move
            gT(i,j,k,bi,bj)   = 0. _d 0
            gS(i,j,k,bi,bj)   = 0. _d 0
out of the #ifdef ALLOW_AUTODIFF_TAMC block
The same for gPtr, but here one has to include PTRACERS.h as well (also 
in a ALLOW_AUTODIFF_TAMC block).

I won't check this in, because appearently nobody ever turn off the 
advection, but maybe that something to keep in mind the next time 
thermodynamics is updated.

Martin

On Monday, September 22, 2003, at 11:06 AM, Martin Losch wrote:

> Hi again,
> I have made an interesting discovery while trying to turn off 
> advection for the passive tracers package:
> When I include a runtime flag, analogous to tempAdvection or 
> saltAdvection, for passive tracers, the tracer model explodes after a 
> few time steps. With advection turned on (the default) everything is 
> okay. I couldn't find the place where the passive tracer gets 
> corrupted (it doesn't happen in ptracers_integrate, 
> ptracers_advection, nor in ptracers_forcing. cycle_tracer and 
> timestep_tracer are not the source of error either.)
> But now this:
> I turned off tempAdvection and saltAdvection (linear equation of state 
> so that salt is passive as well), and you know what, the model 
> explodes, too.
>
> advection schemes are 2 (cented 2nd order) for theta and salt and 33 
> (DST3FL) for the passive tracer package, but that shouldn't matter, 
> should it?
>
> Any idea, what's going on?
>
> Martin
>
> Martin Losch // mailto:mlosch at awi-bremerhaven.de
> Alfred-Wegener-Institut für Polar- und Meeresforschung
> Postfach 120161, 27515 Bremerhaven, Germany
> Tel./Fax: ++49(471)4831-1872
>
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