Waves the size of the ocean

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Waves in the ocean come in many different sizes. One of the largest in length is called the Rossby wave. These waves exist in the Pacific Ocean and travel from east to west. Though they are hundreds of miles long, Rossby waves are only a few inches high and take months to cross the ocean. This false-color movie above shows Rossby waves travelling across the ocean, with the wave heights measured by satellite shown as colors blue or red. A similar effect is created by Kelvin waves, which travel in the opposite direction (west to east). The size and speed of these waves are set naturally and are due to the size and depth of the ocean.

Credit: NASA/JPL - TOPEX/Poseidon

For more info: http://topex-www.jpl.nasa.gov/science/chelton.html