[MITgcm-support] pkg/dic options ?

[David Ferreira]

Hi Alexandre,

In my coupled run, I set #define DIC_NO_NEG. it keeps tracer values 
positive in a few places, just by resetting them to zero if negative 
(which could happen because of overshoot in the advection scheme for 
example). It breaks conservation but is helpful. Importantly, this 
option should not do a lot of work. At least in my experience, tracer 
conservation is good even with it on.
I don't use DIC_BOUNDS.
ALLOW_OLD_VIRTUALFLUX: if you are using the non-linear free surface or 
r*, the dilution by E-P is done naturally, no need to bother.

Can;t say much about the two other options.

cheers,
david


On 8/26/15 10:44 AM, Alexandre Pohl wrote:
> Dear all,
>
> I am using a coupled configuration of the MITgcm with the pkg/dic 
> enabled. My goal is to simulate the loci of high biological 
> productivity in deep-time (450 Ma ago), and to test the influence of 
> the palaeogeographical evolution on the latter.
>
> Though I roughly understand what each flag found in the DIC_OPTIONS.h 
> file means, I am not sure whether I should define them or not. Would 
> you tell me what you suggest concerning :
>
> - DIC_NO_NEG ?
> - and DIC_BOUNDS ?
>
> - ALLOW_OLD_VIRTUALFLUX ? The name, containing 'old', suggests that 
> there is now something better but I did not find anything else that 
> accounts for the dilution of dic and alk by fresh water fluxes in the 
> code. Are you using this virtual flux as Friis et al. (2006, Possible 
> overstimation…, Global Biogeo Cycles) did in their paper?
>
> - CAR_DISS ? There is an illustration of the effect of this specific 
> code in Friis et al., 2006, and in Friis et al., 2007 (Dissolution of 
> calcium carbonate…, Biogeosciences), but I don’t know what is the best 
> alternative for a general case study. Would you use this CAR_DISS code?
>
> - LIGHT_CHL ? Given that I have no chrolophyll climatology for my 
> deep-time study, is it better to use this code with the default value 
> or not using it at all ?
>
> Any help would be highly appreciated, shoud this concern any of these 
> questions.
> Thanks!
> Alexandre
>
>
>
> __
>
> *Alexandre POHL*
> PhD Student
> Laboratoire des Sciences du Climat et de l’Environnement (LSCE)
> Centre d'Etude de Saclay
> CEA-Orme des Merisiers, bât. 701
> F-91191 GIF-SUR-YVETTE CEDEX
> FRANCE
> alexandre.pohl at lsce.ipsl.fr <mailto:alexandre.pohl at lsce.ipsl.fr>
>
>
>
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