DOWNWELLING_PAR from EURO-ARGO to EXV033

[delphinedobler]

Argo R03 is already mapped to P01. I-ADOPT relationship is thus needed betw. P01 and EXV tables for this variable.

PID of Variable: https://vocab.nerc.ac.uk/collection/P01/current/DWIRRXUD/ to link to https://vocab.nerc.ac.uk/collection/EXV/current/EXV033/

Variable Description: Downwelling Photosynthetically Available Radiation (PAR).

Property (label): https://vocab.nerc.ac.uk/collection/S06/current/S0600131/
N.B. S0600131 is already mapped to DWIRRXUD but using the MIN mapping, not the hasProperty iADOPT one.

Object of Interest (label): unsure for light, light or photon is not in S27 table.

Matrix (label): https://vocab.nerc.ac.uk/collection/S21/current/S21S027/

[gwemon]

@delphinedobler I think that we need to review EXV033 and its mappings against I-ADOPT. The EOV specification sheet says that it corresponds to the variables:

• Top-of-atmosphere (TOA) radiance
• Remote sensing reflectance (Rrs(λ))
• Downward spectral irradiance (Ed)*
• Upward spectral radiance (Lu)*
  All are measured from satellites or from above the water body.
  Strictly speaking the EOV "sub-variables" are the only ones we should link to this EXV. However it has also a strong connection with in-situ optical property measurements (e.g. downwelling PAR as you suggest) and pigment concentration in water bodies.
  So for example, we linked EXV033 to concentration of chlorophyll-a but I now believe this could have been a mistake. Concentration of chlorophyll-a should probably be associated with Phytoplankton diversity and biomass (https://vocab.nerc.ac.uk/collection/EXV/current/EXV056/)
  The specification sheet of EXV056 contains a definition of "Phytoplankton biomass" as "Weight (mass as the concentration in grams per liter or cubic meter or [𝛍g l-1, g m-3], or area-integrated [g m-2]) of bulk organic matter, dry organic matter, or often chlorophyll-a and other pigments, or organic carbon or nitrogen)."
  I would be interested to hear your thoughts about this.

[delphinedobler]

@gwemon ,
we have to keep in mind that the specification sheet are often space-observation oriented. This is the reason why (I suppose) we do not have downwelling_PAR in the specification, but it contributes anyway and makes sense to do this mapping.

Regarding chl-a, chlorophyll-a measured by Argo profilers both contribute to Ocean Color (EXV 33) and indeed, the phytoplankton biomass (EXV 56), thanks for spotting this - I've overlooked it.
If you read carefully the Ocean Color specification sheet from GOOS, chlorophyll-a is a derived product. And Argo chl-a data is really used for cross-calibrating the spacecraft's observations and derived product, within CALVAL specific campaigns.

However, is it possible to have two EXV associated to Chl-a ?

[delphinedobler]

additionnal note: the EXV 56 is only part of EOVs and not of ECVs.