The satellites in NASA’s Earth Observing System collect data and imagery for scientific research. The data goes to one of twelve Distributed Active Archive Centers (DAACs) across the United States, where it is processed and distributed to scientists who mine it for clues about our environment.
But sometimes the imagery is remarkable simply for its beauty. When the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite looked down on the Lesser Antilles on August 1, 2013, the combination of sunlight, islands, and wind painted this scene on the surface of the Caribbean Sea. The right side of the image has a milky hue because of sunglint, an optical effect caused by the mirror-like reflection of sunlight off the water surface directly back at the satellite sensor.
Although sunglint washes out many features, it also reveals details about the water surface and atmospheric circulation that are usually hidden. In this case, the sunglint exposed wakes in the atmosphere caused by prevailing winds arriving from the east. The wakes are likely the result of winds roughening or smoothing the water surface behind the islands. The rocky, volcanic islands create a sort of wind shadow—blocking, slowing, and redirecting the air flow. That wind, or lack of it, piles up waves and choppy water in some places and calms the surface in others, changing how light is reflected.
NASA image courtesy LANCE/EOSDIS MODIS Rapid Response Team, GSFC. Caption by Adam Voiland and Michael Carlowicz.