Measuring El Niño

Joint U.S./French TOPEX/Poseidon satellite

Image courtesy JPL/NASA

In August 1992, TOPEX/Poseidon was launched into Earth's orbit by an Ariane 42P rocket from the European Space Agency's Space Center located in Kourou, French Guinea -- the first launch of a NASA payload from this site. From its orbit 1,336 kilometers (830 miles) above the Earth's surface, TOPEX/Poseidon measures sea level along the same path every 10 days using the dual frequency altimeter developed by NASA and the CNES single frequency solid-state altimeter. This information is used to relate changes in ocean currents with atmospheric and climate patterns. Check the most recent sea level readings.

The Tropical Atmosphere Ocean Array

Image courtesy PEML/NOAA

The TAO array consists of approximately 70 ATLAS buoys and current meter mooring sites in the tropical Pacific Ocean, telemetering oceanographic and meteorological data in real-time via the Argos satellite system. Designed to improve detection, understanding, and prediction of El Niño, TAO is a major component of the global climate observing system. The array is presently supported by an international consortium, involving cooperation between the United States, France, Japan, Korea and Taiwan.

Pacific El Niño-Southern Oscillation Applications Center Pilot Project

In the early 1970s, the University of Hawaii Sea Level Center began installing tide gauges in the tropical Pacific to study the potential of sea level observations for ocean monitoring. Using data from this network of gauges, Professor Klaus Wyrtki presented the first detailed descriptions of the oceanic ENSO cycle in the tropical Pacific. Further development of this program over the intervening years has resulted in the Indo-Pacific Sea Level Network, presently the largest open ocean sea level network in the world operated by a single group.

Gathering clues of past El Niños

In addition to running truckloads of data through high speed computers, scientists continue to try to figure out what the past looked like by piecing together bits of historical evidence from many different sources, including:

• sea-surface temperature records. Millions of reports from merchant ships crossing the equator have been collected for over a century. Puerto Chicama on the Peru coast has reported water temperature regularly since the 1930s.
• daily observations of atmospheric pressure and rainfall. Some stations, like the one at Darwin, Australia, have records extending back more than 100 years.
• fisheries' records from South America.
• writings of Spanish colonists in settlements along the coasts of Peru and Ecuador dating back to the late fifteenth century.

Another way scientists can make guesses as to what happened in the past is by looking at coral samples and tree rings, which by their annual growth patterns can potentially provide clues to El Niños of past centuries.