. "The surface called \"surface\" means the lower boundary of the atmosphere. \"Water\" means water in all phases, including frozen i.e. ice and snow. Downwelling radiation is radiation from above. It does not mean \"net downward\". \"Photosynthetic\" radiation is the part of the spectrum which is used in photosynthesis e.g. 300-700 nm. The range of wavelengths could be specified precisely by the bounds of a coordinate of radiation_wavelength. A photon flux is specified in terms of numbers of photons expressed in moles. In accordance with common usage in geophysical disciplines, \"flux\" implies per unit area, called \"flux density\" in physics." . "surface downwelling photosynthetic photon flux in sea water" . "Climate and Forecast (CF)" . . . .