NASA MODIS Image of the Day: January 8, 2007 – Ship-wave-shaped Clouds in the South Pacific Ocean
The cloud patterns seen in this MODIS Terra image, captured on January 2, 2007, are called “ship-wave-shaped clouds”. They are called this because they resemble ship waves (or “Kelvin ship waves”), which are the V-shaped wakes left by moving objects, such as ships or even ducks.
In this case, the cloud patterns were caused by Macquarie Island, the Auckland Islands, and Campbell Island in the South Pacific Ocean. As the wind flows past the islands, it is swept around and over it leaving a wake similar to that of a ship– hence the name “ship-wave-shaped” clouds.
The pattern is not accidental or coincidental, there is a physical reason for it. Wind behaves like a fluid; when it encounters an obstacle, it must move around it, leaving behind a wake (like yesteday’s Von Karmann vortices), or a visible wave pattern. Ship-wave-shaped cloud patterns form as the air alternately cools and warms on the wave peaks and troughs, causing clouds to form on the peaks, but not the troughs.
