How ocean water absorbs and scatters light, near real-time (Sentinel-3A)

The Ocean Biology DAAC produces near real-time (NRT) products using the best-available combination of ancillary data from meteorological and ozone data. As such, the inputs and the calibration used are less than optimal. Near real-time products provide a snapshot of the data during a short time period within a single orbit. The Inherent Optical Properties (IOP) suite provides per-pixel inherent optical properties - quantities that describe how seawater and its constituents absorb and scatter light, independent of illumination or viewing geometry. IOPs are retrieved from spectral Remote Sensing Reflectance (Rrs) using the default configuration of the Generalized Inherent Optical Properties (GIOP) model framework. These products support water-type classification, water-clarity assessment, biogeochemical studies, and forward/adjoint radiative-transfer applications, and they enable more robust cross-sensor comparisons than purely apparent (AOP) products. This activity was informed by the Satellite Needs Working Group (SNWG), an interagency effort of the U.S. Government dedicated to identifying and addressing Earth observation needs across U.S. civilian federal agencies. Geophysical variables in this suite include: - a – Total absorption coefficient (sum of pure water + phytoplankton + CDOM/detritus, m⁻¹) - bb – Total backscattering coefficient (m⁻¹) - l2_flags – Level-2 processing flags (bitmask; see per-variable attributes for flag_masks and flag_meanings). - aph_443 – Phytoplankton absorption coefficient at 443 nm (m⁻¹) - aph_unc_443 – Uncertainty in absorption due to phytoplankton at 443 nm (m⁻¹) - adg_443 – Combined CDOM + non-algal detritus absorption coefficient at 443nm; accompanied by adg_s (spectral slope, units nm⁻¹). - adg_unc_443 – Uncertainty in absorption due to gelbstoff and detrital material at 443 nm (m⁻¹). - bbp_443 – Particulate backscattering coefficient at 443nm (m⁻¹); include bbp_s (power-law slope, unitless) describing spectral shape. - bbp_unc_443 – Uncertainty in particulate backscattering at 443 nm (m⁻¹). - rrsdiff – Fractional mean Rrs difference.