EARTH Aral Sea -- 12 Mar 2009 -- Distinctive lines of clouds stretch out from the shore of the Aral Sea in this photo-like image captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite.

EARTH Aral Sea -- 12 Mar 2009 -- Distinctive lines of clouds stretch out from the shore of the Aral Sea in this photo-like image captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite. While wave clouds like this are not unusual, this particular pattern over the Aral Sea is highly unusual. The clouds conform exactly to the shape of the western shore. Wave clouds typically form when a mountain, island, or even another mass of air forces an air mass to rise. The air cools as it rises, and if there is moisture in the air, the water condenses into clouds. Once the air has gone over the obstacle, it sinks again. The air warms as it drops, and the cloud dissipates. Like ripples on a pond, the wave motion continues, and the air rises and drops again and again until eventually the wave dissipates. The result is a line of clouds marking the crests of the wave, separated by clear areas in the troughs of the wave -- Picture by Lightroom Photos / NASA