English: Reflected sunlight and gusting wind combined to create a beautiful scene in the Arabian Sea in mid-April 2017. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite acquired this true-color image on April 11.

The silvery hue of the water is due to “sunglint”, which is an optical effect caused by the mirror-like reflection of sunlight off the water surface directly back at the satellite sensor. Sunglint can be a nuisance in remote sensing as the brightness can hide many features, but it can also be a bonus when it reveals details about water movement or water/wind interactions.

When the ocean surface is very smooth it acts like a mirror, reflecting light back towards the sensor in a very uniform fashion. When the ocean surface is rough, however, the light hitting the water is scattered in different directions, with little or none returning directly to the sensor. Therefore, when surface winds are very strong and create rough water, sunglint is diffuse and pale – and when seas are very rough, water appears dark. Conversely, where winds are light, sunglint appears bright.