Topex/Poseidon data

Sea surface measurements taken by the U.S./French TOPEX/Poseidon satellite have confirmed that conditions are ripe for development of an El Nio event in the eastern equatorial Pacific Ocean this winter.

Data from the radar altimeter onboard TOPEX/Poseidon reveal a new Kelvin wave moving toward the western coast of South America. A Kelvin wave is a large warm water mass that moves along the equator in the Pacific Ocean. Such Kelvin wave pulses sometimes give rise to El Nio conditions in the eastern equatorial Pacific.

Using near real-time data from TOPEX/Poseidon, this most recent wave pulse has been confirmed by Drs. Jim Mitchell and Gregg Jacobs of the Naval Research Laboratory (NRL) at NASA's Stennis Space Center in Mississippi.

"This wave was generated in early August at the equator around 160 East longitude and moved eastward in the form of a bulge of sea surface elevation of 10 to 15 centimeters above normal," said Jacobs.

The Kelvin wave pulse which began in August may have faded in strength in early October. At this time, the rise of sea surface in the west is indicative of the onset of a stronger Kelvin wave.

The NRL team continues to monitor these developments in addition to using numerical ocean models to better understand the evolution of the Kelvin wave's strength, Mitchell said.

The data confirm an advisory issued recently by the National Oceanographic and Atmospheric Administration's Climate Analysis Center that El Nio conditions would continue in 1993-94.

This Kelvin wave, plus other oceanographic and meteorological indicators, has indicated a strong potential for the redevelopment of the El Nio conditions that have persisted through two consecutive winters in 1991 and 1992, according to the NOAA advisory.

"The rise of warm water hinders cold deep waters from reaching the surface. Off the coast of South America, cold deep waters bring vital nutrients to sea life. When the Kelvin wave reaches South America, the deep waters no longer reach the surface and the fish stocks become severely depleted," according to Jacobs.

The El Nio phenomenon has been blamed for causing devastating weather conditions around the world including severe floods in the Midwest, colder than normal winters in the eastern United States and wetter than normal conditions in California.

The TOPEX/Poseidon mission is addressing long-term climate issues. By mapping the circulation of the world's oceans over several years, scientists can better understand how the ocean transports heat, influences the atmosphere and affects long-term climate, said Dr. Lee-Lueng Fu, TOPEX/Poseidon project scientist at JPL.

Data from the satellite are distributed monthly for analysis by more than 200 scientists around the world.

JPL manages the NASA portion of the joint U.S./French TOPEX/Poseidon mission. Launched Aug. 10, 1992, it is the second satellite in NASA's Mission to Planet Earth program, a long-term effort to study Earth as a global environmental system.

News Media Contact