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Re: Biotic HOWTO



On Mon, 1 Feb 1999, Ray Najjar wrote:

> Keith, thanks for your comments.
> 
> >   1) No special allowance is made for negative tracer concentrations. In the
> >   current version of our code here, we treat these values as zero.
> 
> The problem here is that you can change your phosphate inventory as a result
> of this.  If you add phosphate (by setting negative PO4 values to zero) then
> you should remove it elsewhere, perhaps uniformly throughout the model.
>   

I did not explain myself well on this point. We do not set negative tracer
concentrations to zero. What we do is to treat them as if they were zero
in the biological source/sink computations. This is particularly of
interest for the kappa * [DOP] term of equations 25 and 28, which
represents conversion of DOP to PO4 due to consumption. We do not think
that negative values of [DOP] should imply that this process is reversed,
so we treat the values as zero. But we do not actually change the values
of [DOP]. Does this approach sound appropriate to you? I do not think that
it presents problems for conserving inventory.

***********************************************************************
Keith Lindsay                              phone: 303-497-1722
Climate and Global Dynamics                fax:   303-497-1700
National Center for Atmospheric Research   email: klindsay@cgd.ucar.edu
P.O. Box 3000
Boulder, CO  80307-3000