Issue about the formula to calculate light effect on algae growth

System Modules WAQTEL / AED2
1

Hello,

According to the source code of waqtel/ray_effect.f and WAQTEL theory guide, the light effect on algae growth was calculated by Smith formula shown in the Figure attached, but it is averaged over the depth for now.

!     warning: the formula of smith is depth integrated, here after a tentative

!              generalization, to be investigated later.

      DO KK=1,NPOIN

        CC=H%R(KK)*T1%R(KK)

        IF(CC.GT.EPS)THEN

          EFF%R(KK)=LOG(CNUM/(T2%R(KK)+SQRT(IK2+T2%R(KK)**2)))/CC

        ENDIF

      ENDDO

For 3D models this generalization would probably lead to unreal Chla results, so does anyone know how to modify the code above to make sure the ray effect varies along the depth?

Besides, where can we find the reference of the original [name removed] formula? It’s neither listed in the user_manual/theory_guide nor the source code.

Many thanks,

Yunhao

Smith.png
Smith.png990×253 22.5 KB

2

Hello [name removed],

The BIOMASS and EUTRO modules were previously developed for the 1D code MASCARET/TRACER (1D Shallow Water Equations), then extended to TELEMAC-2D for Shallow Waters Equations and TELEMAC-3D, that is why you have this formulation. It is not obvious what to do to extent a depth averaged view to 3D, that is why I think the previous WAQTEL carer added this comment.

I am not a specialist of water quality, it is not easy to give the right answer.

Anyway, it seems that this Smith formula may come from an old paper you can get here, but I am not sure:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1079215/pdf/pnas01772-0045.pdf

Hope this helps,

[name removed]

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