Improving the Description of Sunglint for Accurate Prediction of Top-of-the-Atmosphere Radiances

The ocean bidirectional reflection distribution function (BRDF) 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 we can describe the ocean BRDF. Existing models predict the Sunglint-generated contribution essentially expressing it as a function of the wind speed, thus so is also the extent of the glint-contaminated region. An accurate treatment of the glint-contribution would improve current correction schemes and hence rescue a significant portion of data presently discarded as "glint contaminated". In the SeaDAS imagery correction schemes, an attempt to correct the sensor-measured radiances is limited to the region at the edge of the glint where the contribution is below a certain threshold. Yet, this correction assumes the Sunglint component to be directly transmitted through the atmosphere. To quantify the error introduced by this approximation we employ a radiative transfer code that allows for a user-specified BRDF at the atmosphere-ocean interface and rigorously accounts for multiple scattering. Since this model describes more accurately the physics of the problem, its inclusion in the atmospheric correction procedure enables more reliable calculation of the glint radiance for an extended portion of the glint-contaminated region, resulting in fewer pixels being rejected during retrievals. Here we report on a parametrization of our model that will make the glint correction more efficient and computationally inexpensive when deriving ocean and atmospheric products from satellite imagery, and we present preliminary results demonstrating the merit of this approach.