This astronaut photograph illustrates the formation of wave clouds in the wake, or downwind side, of ÃŽle aux Cochons, often called Pig Island, in the southern Indian Ocean. The island's summit elevation is high enough to interact with cloud layers and flowing winds. Once air masses pass over the summit, they descend and may encounter alternating moist and dry air layers, enabling the formation of the discontinuous, chevron-shaped wave clouds.