The spectral diffuse attenuation coefficient of downwelling irradiance (Kd). Kd is an apparent optical property (AOP) that is derived from IOPs using the Lee bio-optical model. Kd describes how visible light diminishes with depth in the ocean. Lower values indicate clearer water (deeper light penetration); users commonly apply Kd to estimate euphotic depth, track coastal water quality and turbidity, interpret bloom/light environments, and supply inputs to biogeochemical and ecosystem models. As with all ocean-color products, uncertainties can be larger in optically complex coastal or inland waters; refer to the file metadata and algorithm documentation for quality flags and usage notes.

Geophysical variables in this suite include:

• Kd — Diffuse attenuation coefficient of downwelling irradiance, Lee algorithm (m⁻¹)