spm effect on density

[Knut]

Dear Jorn,

we would like to add the density effect of spm to our simulations. What
do you think is the best solution for fabm/gotm/getm? We thought about a
density correction calculated in fabm and applied in gotm. the density
from getm could be modified by gotm_fabm and the result will not be
overwritten by the equation of state, because that was called on the
getm side before do_getm_fabm().

Best, Knut

[Knut]

On 2/24/20 5:12 PM, Karsten Bolding wrote:

but I think iow_spm is about to be obsolete as it has not been updated to the new FABM requirements - or is there another SPM module ....

yes, this is another construction site...

Hans was looking for one Friday.

and talked to Ulf and me today. We will come up with an updated version.

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Karsten Bolding

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+4564422058

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[Jorn Bruggeman]

Hi Knut,

There are some examples of density feedbacks in FABM that I've worked on with Ole Anders Nost (Akvaplan-niva) and Evgeniy Yakushev (NIVA) in FVCOM:

* We've looked at the impact of fluids with different density injected into the water. There the feedback was implemented by assuming conservation of volume when the fluid mixes with the water. The variables passed back to FABM were the "non-water fraction of volume" and the density of that non-water fraction. FVCOM's final density was constructed by combining the value from its EoS and the non-water contribution.https://github.com/fabm-model/fabm/blob/master/src/models/akvaplan/tracer.F90.
* We've looked at hypersaline systems where salinity increases up to the point where different salts starts to precipitate out of the water. In that case we've used FABM to track the concentration of different ions that make up "salinity", and FABM passed back a "mass_concentration_of_solute" that overwrote the FVCOM salinity. https://github.com/fabm-model/fabm/blob/master/src/models/niva/brom/brom_salt.F90

I know, neither of these cases exactly matches your requirements, but they do illustrate how feedbacks can be implemented: typically you let your FABM module contribute to some "aggregate variable", which can then be picked up by the host (GOTM/GETM). For BGC configurations where the feedback is absent, that aggregate variable will have value 0, which ideally would automatically disable the feedback.

For your SPM case, I'd imagine the FABM SPM module can let its variables contribute to an aggregate variable "mass_concentration_of_suspended_matter" (kg/m3). GOTM can request the total of this variable and store it (a pointer to it) at module level. GETM then needs to pick that up to construct the full 3D density perturbation. It makes sense to me to then add it to the existing density in kg/m3.

Cheers,

Jorn

[Knut]

Dear Jorn,

thanks a lot for your fast feedback. We will look into your examples and
come back to you.

Regards, Knut