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NH4-NO3 uptake fraction

VY
veli yumruktepe, modified 5 Years ago.

NH4-NO3 uptake fraction

Padawan Posts: 42 Join Date: 2/7/12 Recent Posts
Hi all,

I was wondering whether we can define an uptake ratio of NH4 & NO3? Can this be set to modify in processes menu. I have seen in manuals that this ratio is called "fam" i think. What is the default value and is there a way we can modify it without changing the code and recompiling it?

Thanks
Michel Jeuken, modified 5 Years ago.

RE: NH4-NO3 uptake fraction

Jedi Knight Posts: 156 Join Date: 1/21/13 Recent Posts
Dear Veli,

I assume you mean the uptake of NH4 & NO3 by algae. In tha manual you can also read:

"The fraction of ammonium in nitrogen nutrients consumed fam simply follows from the total demand for the nitrogen nutrients and the current ammonium and nitrate concentrations. If the demand is not covered by ammonium alone, the model allocates the additional demand to nitrate."

So 'fam' or 'fraction ammonium' is only the result of the available nutrients, and is 1.0 if enough ammonium is available. The assumption is that algae only take up nitrate when there's no ammonium around.

We have two algae models (BLOOM & DYNAMO). Although you can't set a preference in both you can force algae to take up more nitrate by setting a critical NH4 level ThrAlgNH4 (in BLOOM) or NH4KRIT (in DYNAMO, process NutUpt_Alg). If you want to do it differently you will need to modify the code.

For BLOOM look into \src\engines_gpl\waq\packages\waq_kernel\src\bloom\blprim.f line 382:383 it states

C Correct for depletion of NH4 assume that
C phytoplankton first depletes ammonia (completely)

Below those lines you can modify it the uptake preference. The critical ammonium and nitrate lavels are already deducted here.

In the DYNAMO model look at \src\engines_gpl\waq\packages\waq_kernel\src\waq_process\nutupt.f

Michel
VY
veli yumruktepe, modified 5 Years ago.

RE: NH4-NO3 uptake fraction

Padawan Posts: 42 Join Date: 2/7/12 Recent Posts
Dear Michel,

I indeed mean the uptake by algae. I think your answer was what i was looking for. I guess for the time being I will use the tresholds for the NH4 uptake and work with the code if necessary.

Thanks for the input.

Veli