Photosynthetic photon flux density (PPFD)
The number of photons per unit time and per unit area in the wavelength band 400 to 700 nm
Wikipedia
https://en.wikipedia.org/wiki/Photosynthetically_active_radiation
Added to support Critical Zone Observatory (CZO) data use cases.
ODM2 Variable Name Controlled Vocabulary
ODM2 Working Group
A vocabulary for describing the name of Variables.