[MITgcm-support] bug in DIC package

[Martin Losch]

Hi Christoph,

I would go so far as to say, that the computation of gsm_s, etc, which  
currently takes place in gchem_forcing_sep (and is thus never done  
when dic_surfforcing_init is called), should be moved into  
dic_forcing_biotic, and then also into dic_surfforcing_init, but I  
don't use this package and I don't know if there are other things to  
consider.

Martin
On Feb 19, 2009, at 11:48 AM, Christoph Voelker wrote:

> Hi,
>
> I think I have found a small bug in dic_surfforcing_init.F (using  
> last weeks cvs checkout of MITgcm). The bug only matters when you do  
> not set DIC_BIOTIC (which I did inadvertently), so it is probably  
> unimportant in most cases. Anyway, it shouldn't be there, so here is  
> my description
>
> The following lines in dic_surfforcing_init.F set the initial  
> concentrations of alkalinity and phosphate for calculating the  
> initial discribution of CO@ partial pressure. if DIC_BIOTIC is not  
> set, alkalinity is set proportional to salinity.
>
> #ifdef DIC_BIOTIC
>             surfalk(i,j) = PTRACER(i,j,klev,bi,bj,2)
>     &                          * maskC(i,j,kLev,bi,bj)
>             surfphos(i,j)= PTRACER(i,j,klev,bi,bj,3)
>     &                          * maskC(i,j,kLev,bi,bj)
> #else
>             surfalk(i,j) = 2.366595 _d 0 * salt(i,j,kLev,bi,bj)/gsm_s
>     &                          * maskC(i,j,kLev,bi,bj)
>             surfphos(i,j)= 5.1225 _d -4 * maskC(i,j,kLev,bi,bj)
> #endif
>
> However, at this point the global mean salinity gsm_s is not yet  
> defined, so the calculation produces infinity. I think this has to  
> do with the order in which the initializations for the different  
> packages are done.
>
> Cheers, Christoph
>
> -- 
> Dr. Christoph Voelker / Alfred-Wegener Institute for Polar and  
> Marine Research
> email: cvoelker at awi-bremerhaven.de / tel.#: ++49 471 4831 1848 /
> mail: PO Box 120161, 27515 Bremerhaven, Germany
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