[MITgcm-support] New user with problems with ptracers

[cimatori at libero.it]

We begin to have some reasonable results. I think the problem lied also in making a simulation too ideal (costant field in the plane, open periodic domain) and too short.
Thanks
Andrea

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>From      : mitgcm-support-bounces at mitgcm.org
To          : mitgcm-support at mitgcm.org
Cc          : 
Date      : Wed, 22 Sep 2004 09:45:18 +0200
Subject : Re: [MITgcm-support] New user with problems with ptracers

> Hi Andrea,
> 
> your version of the code should work, but an upgrade wouldn't hurt 
> either ...
> I have two guesses of what could be going on:
> 1. There are two routines, ptracers_forcing.F and 
> ptracers_forcing_surf.F, where the passive tracers get their forcing 
> (the surface forcing is set in the latter and that is added to the 
> overall forcing in the former). For testing purposes the forcing for 
> all tracers is identical to that of salinity (surfaceTendencyS in 
> ptracers_forcing_surf.F), so that all passive tracer are identical to 
> salinity, except that they are passive. If you want to do something 
> sensible with ptracers, you should, in ptracers_forcing_surf.F set 
> surfaceTendencyPtr=0 or to whatever makes sense in your configuration, 
> for example, you could specify a source of tracer (polution by a 
> river?) here. For deep sources you need to modify ptracers_forcing.F. 
> Also you need to specify an initial conditions file for your passive 
> tracer, otherwise it's all zeros (but you probably have done that).
> 2. by default the turbulent mixing (diffusion) coefficients of all 
> passive tracers equal those of salinity. There is little reason to 
> assume different turbulent mixing coefficients for different passive 
> tracers (even if they have different molecular diffusion coefficients). 
> At the moment it's even quite difficult, or even impossible, to make 
> the VERTICAL diffusivity (ptracers_diffkr) for ptracers different from 
> that of salinity, especially if you are using a mixed layer model 
> (KPP). I would not try that. The HORIZONTAl diffusivity parameters 
> (ptracers_diffkh/diffk4) should have an effect.
> I agree that the availability of all these runtime parameters is a 
> little confusing.
> 
> I am quite confident that the first point (removing salinity forcing in 
> ptracers_forcing_surf) will fix your problem.
> Martin
> 
> On Sep 21, 2004, at 5:20 PM, cimatori at libero.it wrote:
> 
> > Hi, I'm a new MITGCM user from Italy. I'm working for my third year 
> > thesis at the OGS in Trieste (Italy), with Stefano Querin and Cosimo 
> > Solidoro.
> > We want to set up a model for Trieste Gulf using ptracers package too, 
> > we tried using checkpoint 52.e_pre, with minor changes but we get 
> > strange results. All the tracers behave just like salt (or nearly like 
> > salt), even if we changed diffKh by 10^3. We also get always the same 
> > results (and in the same order), changing parameters.
> > Do you think that trying with a newer version could work?
> > Thanks.
> > Andrea Cimatoribus
> >
> >
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> >
> Martin Losch // mailto:mlosch at awi-bremerhaven.de
> Alfred-Wegener-Institut für Polar- und Meeresforschung
> Postfach 120161, 27515 Bremerhaven, Germany
> Tel./Fax: ++49(471)4831-1872/1797
> http://www.awi-bremerhaven.de/People/show?mlosch
> 
> 
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