ABSTRACTS

Oral Session 7 | Wednesday, October 5, 12:00–12:20 | Abstract 615

Sea-surface reflectance factor: spectral and atmospheric dependence

The sea-surface reflectance factor rho, which is required for the determination of the water-leaving radiance from above-water radiometric measurements, was computed through radiative transfer simulations for various atmospheric and sea surface conditions in the 350-1020 nm spectral interval. The simulations were performed with the Monte Carlo code for Ocean Color Simulations (so-called MOX) by ingesting sky radiance data simulated with the Finite Element Method (FEM) radiative transfer code. The considered measurement geometry is that recommended in protocols for the validation of satellite ocean color data, and commonly applied for operational measurements. Results indicate that the dependence of rho on wind speed and sun elevation decreases with the atmospheric optical thickness, and additionally show an increase with wavelength. For typical atmospheric conditions, wind speed lower than 4 m/s and sun zenith angles larger than 20 degrees, the variation of rho in the 412-681 nm spectral interval is up to 4% with respect to the value determined at 551nm. When the atmospheric variability is also accounted for, the overall percent variation of rho is up to 5.6%. When relaxing the constraints on sun elevation, wind speed and wavelength, the percent variation of rho with respect to the value determined at 551nm might exceed 100%. A benchmark of the newly simulated rho values with those formally determined with Hydrolight and widely used by the ocean color community, exhibits systematic differences whose source is discussed, and implications for field measurements are addressed.

Barbara Bulgarelli, European Commission – Joint Research Centre, 0000-0002-9668-2469

Davide D’Alimonte, AEQUORA, 0000-0001-7217-7057

Giuseppe Zibordi, European Commission – Joint Research Centre, 0000-0002-2253-1828

Tamito Kajiyama, AEQUORA, 0000-0002-3148-9705