Have you ever wondered what that large bright area is over open ocean waters that moves east to west during the day at lower latitudes? As you may have guessed, this phenomenon known as “sun glint” is due to large reflections of the sun off of water surfaces when the sun and satellite are properly aligned. The sun’s reflection is apparent over a given area when the sun-earth and satellite-earth angles are the same, much like viewing an object in a mirror. Sun glint is observed in the visible and near-IR bands of GOES-16, and is most noticeable at longer wavelengths where scattering due to atmospheric aerosols is not as abundant. The reflection is greatest over smooth surface waters, and weaker over rough surface waters where sunlight is reflected in multiple directions leading to less direct sunglight making it back to the satellite. In addition to differentiating smooth vs rough ocean surfaces, sun glint may be used to detect ocean currents and internal waves.
Below is an example of sun glint from the “preliminary, non-operational” GOES-16 0.86 um near-IR channel on 3/15/2017. Full disk, 15-min imagery is shown over the lower latitudes.
-Bill Line, NWS
“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”