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FOR IMMEDIATE                                                 January 24, 1995

       Scientists studying data from the ocean-observing TOPEX/Poseidon satellite say they are seeing conditions in the equatorial Pacific that indicate El Niņo is back and getting stronger.

       El Niņo is a climatic event that can bring devastating weather to several parts of the world, including the recent heavy rains and flooding in California and the warmer than normal winter in New England.

       "The satellite has observed high sea-surface elevation which reflects an excessive amount of unusually warm water in the upper ocean," said Dr. Lee-Lueng Fu, TOPEX/Poseidon project scientist at NASA's Jet Propulsion Laboratory. "The associated excess of heat creates high sea-surface temperatures, which affect the weather worldwide by heating the atmosphere and altering the atmospheric jet stream."

       Jet streams are high-level winds, eight to ten kilometers (five to ten miles) above the Earth's surface, created when warm and cold air masses meet. Shifts in the location of jet streams change temperatures and precipitation zones at the surface.

       El Niņo begins when the westward trade winds weaken and a large warm water mass, called a Kelvin wave, is allowed to move eastward along the equator in the Pacific Ocean. Data from the radar altimeter onboard TOPEX/Poseidon, taken during three months from October through December 1994, reveal a new Kelvin wave moving toward the western coast of South America.

       "This wave is currently occupying most of the tropical Pacific Ocean," Fu said. "It will take another month or two before the wave disperses. Compared to the El Niņo condition of the winter of 1992-1993, the present one appears somewhat stronger and might have stronger and longer lasting effects."

       TOPEX/Poseidon, a joint program of NASA and the Centre Nationale d'Etudes Spatiales, the French space agency, uses a radar altimeter to precisely measure sea-surface height. Scientists use the TOPEX/Poseidon data to produce global maps of ocean circulation. Launched Aug. 10, 1992, the satellite has completed two-and-a-half years of its three-year prime mission and has provided oceanographers with unprecedented global sea level measurements that are accurate to better than five centimeters (two inches).

       "The global sea-surface elevation information provided by TOPEX/Poseidon is unique because it is related to the amount of heat stored in the upper ocean, which is important for long-range weather forecasting. The speed and direction of ocean currents can also be determined from the elevation information, providing another piece of critical information about the ocean, which is the key to climate change," Fu continued.

       TOPEX/Poseidon is part of NASA's Mission to Planet Earth, a coordinated, long-term research program to study the Earth as a single global environment. TOPEX/Poseidon's sea-surface height data are essential to understanding the role oceans play in regulating global climate, one of the least understood areas of climate research. TOPEX/Poseidon will provide the first comprehensive, consistent measurements of the circulations of the ocean.

       The Jet Propulsion Laboratory manages the TOPEX/Poseidon mission for NASA's Mission to Planet Earth, Washington, D.C.


1/24/95 MAH

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