Oct. 22, 1998 The latest measurements of sea surface height made by the TOPEX/Poseidon satellite show the tropical Pacific Ocean seesawing between El Nino and La Nina as these two strong conditions battle for dominance.
The new image shows that sea level across the tropical Pacific has essentially maintained the same pattern since mid- June 1998. Remnants of the high sea level, warmer El Nino waters still linger to the north of the equator while the area of low sea level, or cold water that is sometimes referred to as La Nina, remains in the center of the Pacific. It is still uncertain, scientists say, if the ocean is headed toward a long- lasting La Nina situation.
The image shows sea-surface height on October 12, 1998, relative to normal ocean conditions. Sea surface height is an indicator of the heat content of the ocean; the pool of cold water in the Pacific is detected by the satellite as a region of lower than normal sea level. The tropical Pacific Ocean continues to exhibit the complicated characteristics of both a lingering El Nino, and a possibly waning La Nina situation. The coexistence of these two contrasting conditions indicates that the ocean and the climate system remain in transition. These strong patterns have remained in the climate system for many months and will continue to influence weather conditions around the world in this fall and winter.
A La Nina is essentially the opposite of an El Nino condition, but during a La Nina the trade winds are stronger than normal and the cold water that normally exists along the coast of South America extends to the central equatorial Pacific. Like El Nino, a La Nina situation also changes global weather patterns, and is associated with less moisture in the air resulting in less rain along the west coasts of North and South America.
The October 12 image is now available online at:
The U.S.-French TOPEX/Poseidon mission is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, CA, for NASA's Earth Sciences Enterprise, Washington, DC.
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