The Kd_490 product quantifies how quickly blue-green light (490 nm) diminishes with depth—an indicator of water clarity and the depth to which sunlight penetrates. Kd_490 is generated from ocean-color reflectance using the KD2 algorithm. Lower values indicate clearer water (deeper light penetration); users commonly apply Kd_490 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_490 — Diffuse attenuation coefficient at 490 nm, KD2 algorithm (m⁻¹)