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Recent warming event in the Pacific may be an El Niño

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Abstract

A recent anomalous warming event in the tropical Pacific consists of a series of intraseasonal episodes, observations from four spaceborne sensors and simulation by an ocean general circulation model show. Four distinct groups of equatorial westerly wind anomalies near the date line were observed by scatterometer from July through December 1994. The wind anomalies initiated eastward propagating, downwelling Kelvin waves. These waves, in turn, caused a rise in sea level that was registered by an altimeter. Surface-warming episodes related to the Kelvin waves were observed by a visible-infrared radiometer.

Unlike the El Niño events of the 1980s, equatorial warming events in the 1990s are more frequent, last for shorter periods, and are less intense. Whether the 1994 warming can be classified as an El Niño is being debated.

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