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[music throughout]

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El Nino, the world's biggest climate
phenomenon,

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returned stronger than ever in 1997.

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Satellite, ship, and buoy
observations show the onset of this

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warming of the eastern Pacific Ocean as
early as May.

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El Nino globally changes

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precipitation and temperature patterns,
often with destructive results.

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Visualizing how three key datasets
differ from normal conditions reveals

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the magnitude of the 1997-98 event and
gives new insights into how the ocean

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and atmosphere couple to produce El Nino.

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First, we look at sea surface height.

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The gray sheet rises and dips as much as 
30 centimeters from normal.

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Next, we map sea surface temperature.

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Red is 5 degrees Celsius above normal and blue 5 degrees below normal.

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Finally, black arrows are added to mark sea surface winds.

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A weakening of the trade winds in the
far western Pacific fuels an eastward moving wave.

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Sea level is raised as the
windswept wave progresses.

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The wave's arrival at the South American coast
reduces the normal upwelling of cold

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water and warms the surface by as much
as 5 degrees Celsius.

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Intense atmospheric convection, 
associated with equatorial ocean warming,

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causes local winds to converge,

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abating the trade winds' strength and extending the warm pool of water into the eastern Pacific.

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Beneath the ocean surface, warm and cold waters

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are separated by the thermocline, a
boundary at 20 degrees Celsius.

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El Nino flattens the thermocline,
squeezing the warm bulge of water

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eastward into a long shallow pool.

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As scientists collect more detailed data

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through efforts such as NASA's Earth
Observing System, visualization will be

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crucial in probing the elaborate
interactions and far-flung effects of

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future El Ninos.

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[music]