Remote Sensing Reflectance (Rrs)

Remote-sensing reflectance, Rrs, is the ratio of water-leaving radiance to downwelling irradiance just above the sea surface, the fundamental ocean-color quantity after atmospheric correction removes the atmospheric signal. It has units of inverse steradians and describes the spectral shape and magnitude of light scattered back out of the water, which depends on phytoplankton, colored dissolved organic matter, and suspended sediment. Rrs is the input to bio-optical algorithms that retrieve chlorophyll-a, particulate organic carbon, and water clarity. Sensors such as MODIS, VIIRS, and Sentinel-3 OLCI report Rrs across visible bands, and its accuracy hinges on the aerosol optical thickness used in atmospheric correction.