Improved Description of Sunglint for Accurate Prediction of Remotely-Sensed Radiances

Matteo Ottaviani, Stevens Institute of Technology, mottavia@stevens.edu
Robert Spurr, RT Solutions, rtsolutions@verizon.net
Knut Stamnes, Stevens Institute of Technology, kstamnes@stevens.edu (Presenting)
Wei Li, Stevens Institute of Technology, wei.li@stevens.edu
Wenying Su, NASA, Langley Research Center, w.su@larc.nasa.gov
Warren Wiscombe, NASA, Goddard Space Flight Center, warren.j.wiscombe@nasa.gov

The bidirectional reflection distribution function (BRDF) of the ocean is a critical boundary condition for radiative transfer calculations in the coupled atmosphere-ocean system. In remote sensing applications, the ability to retrieve information from the ocean and the overlying atmosphere therefore depends on how accurately the ocean BRDF is described. Existing models express the extent of the glint-contaminated region and its contribution to the radiance essentially as a function of the wind speed. An accurate treatment of the glint contribution and its propagation in the atmosphere would improve current correction schemes and hence rescue a significant portion of data presently discarded as 'glint contaminated'. In current satellite imagery, a correction to the sensor-measured radiances is limited to the region at the edge of the glint, where the contribution is below a certain threshold. This correction assumes the sunglint radiance to be directly transmitted through the atmosphere. To quantify the error introduced by this approximation we employ a radiative transfer (RT) code that allows for a user-specified BRDF at the atmosphere-ocean interface and rigorously accounts for multiple scattering. We show that the errors incurred by ignoring multiple scattering are very significant and typically lie in the range 10-90%.