NASA MODIS Image of the Day: May 14, 2011 – Wave clouds in the Arabian Sea
An intricate pattern of dust and clouds illustrate strong winds blowing over the Arabian Sea, and creating a formation known as wave clouds.
The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite captured this true-color image on May 6, 2011.
Across the center of the image lines of clouds lie in parallel rows off the coast of Oman. The clouds are forming at the crests of waves within the atmosphere. As dry wind blows towards the southeast it pushes into a wall of warmer, moist air that lies over the Arabian Sea. As these two air masses collide, the cool air pushes under the warmer layer, causing it to rise. As the warm air rises, it loses heat and cools, and falls again. These undulations cause a wave effect in the atmosphere. At the top of the high-altitude waves, the colder air cannot hold as much moisture as warmer air, and the clouds form by condensation. Although this is a complex event, when seen from space, the result is a simple, but beautiful white and blue pattern across the ocean. North of these cloud waves, and almost perpendicular to them, the air is also disturbed. In this case, the atmospheric undulations can be seen in both clouds and waves. A few thin streaks of clouds are visible overlying light-colored waves on the ocean surface, while dark bands in the ocean can be seen through clear skies between the clouds. The clouds are forming at the peak of the atmospheric wave. Underneath these peaks, the ocean is undisturbed, because the peak of the wave is far above the water’s surface. Because this area of ocean is in sun glint, an area where the sun reflects off the ocean into the sensor, the smooth surface appears quite light colored, like a mirror. In contrast, where the wave troughs, the sky is cloudless. Here the atmospheric wave touches the ocean surface, disturbing it and dispersing light. Because the surface is disturbed, light is not reflected back and the ocean appears dark.
