Evaluation of sun glint models using MODIS measurements

To understand the performance of various sun glint models, we have carried out comparison studies with measurements from Moderate Resolution Imaging Spectroradiometer (MODIS) for several popular sun glitter models, including the Cox-Munk models, Ebuchi-Kizu models, Breon-Henriot models, etc., over the open oceans using MODIS data at the near-infrared (NIR) (859 nm) and shortwave infrared (SWIR) bands (1240 and 2130 nm). Sun glint models with and without a wind direction dependence were evaluated. To obtain the MODIS-measured glint reflectance from the total reflectance at the top of the atmosphere, we performed atmospheric corrections to remove the effects of atmospheric absorption as well as radiance contributions from molecules (Rayleigh scattering) and aerosols. We have selected 12 MODIS sun glint scenes over various open ocean regions for this study. Our results indicate that overall, the Cox-Munk [1] model with the wind direction dependence has the best performance in terms of correlation coefficients with the MODIS measurements. The Breon-Henriot [8] model performed similarly as from the Cox-Munk model as two models are in fact very close. Findings from these evaluations can improve our ability to accurately remove the sun glint contamination in MODIS imagery and produce robust satellite ocean color and atmosphere products.