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El Nino, the world's biggest climate phenomenon,
returned stronger than ever in 1997.
Satellite, ship, and buoy observations show the onset of this
warming of the eastern Pacific Ocean as early as May.
El Nino globally changes
precipitation and temperature patterns, often with destructive results.
Visualizing how three key datasets differ from normal conditions reveals
the magnitude of the 1997-98 event and gives new insights into how the ocean
and atmosphere couple to produce El Nino.
First, we look at sea surface height.
The gray sheet rises and dips as much as 30 centimeters from normal.
Next, we map sea surface temperature.
Red is 5 degrees Celsius above normal and blue 5 degrees below normal.
Finally, black arrows are added to mark sea surface winds.
A weakening of the trade winds in the far western Pacific fuels an eastward moving wave.
Sea level is raised as the windswept wave progresses.
The wave's arrival at the South American coast reduces the normal upwelling of cold
water and warms the surface by as much as 5 degrees Celsius.
Intense atmospheric convection, associated with equatorial ocean warming,
causes local winds to converge,
abating the trade winds' strength and extending the warm pool of water into the eastern Pacific.
Beneath the ocean surface, warm and cold waters
are separated by the thermocline, a boundary at 20 degrees Celsius.
El Nino flattens the thermocline, squeezing the warm bulge of water
eastward into a long shallow pool.
As scientists collect more detailed data
through efforts such as NASA's Earth Observing System, visualization will be
crucial in probing the elaborate interactions and far-flung effects of
future El Ninos.
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