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El Niño and La Niña

El Niño and La Niña are part of a climate cycle referred to as the El Niño -Southern Oscillation (ENSO). During El Niño, warmer than average sea surface temperatures occur in the Equatorial central and eastern Pacific while during La Niña, cooler than average sea surface temperatures predominate. The Southern Oscillation ("SO" in ENSO) represents the atmospheric component of the cycle in which lower (higher) than normal sea-level pressure occurs near Tahiti and (higher) lower sea-level pressure occurs in Australia during El Niño (La Niña) conditions. ENSO is an important component of the climate system since the El Niño/La Niña phases impact weather on a global scale.

The impact of ENSO sea surface temperatures (SSTs) on the atmosphere is through the tropical response of rain-producing convection and cloud formation, the principal agents for exchanging heat from Earth's surface. Normally, the SST is very warm in an area that covers the equatorial Indian and west Pacific Ocean regions. During El Niño, the eastern and central equatorial Pacific warms causing rainfall to shift several thousand kilometers east from the western equatorial Pacific in response to the warming of the underlying SSTs. The opposite occurs during La Niña, with rainfall deficits in the eastern equatorial Pacific and wet conditions confined to the western equatorial Pacific.

The strong El Niño of 1982/83 has inspired innovative climate research, which has resulted in greater predictability of El Niño/La Niña. To serve society's need for weather and climate information and to help plan and respond to weather and climate impacts, NOAA's research laboratories have taken a leadership role in furthering ENSO observations and research to improve understanding, predictions, and impacts.

Why we study ENSO

ENSO causes widespread impacts on a global scale such as, drought, wildfires, crop failure, starvation, increased tropical storm/hurricane activity, damage to ecosystems, flooding, and increased spreading of infectious diseases.

Understanding and predicting ENSO has resulted in more accurate climate predictions and, therefore, a reduction of its impacts through better planning. Decision-makers are able to more effectively manage agricultural and water resources, fisheries, and grain and fuel reserves.

How we study ENSO

NOAA's research labs provide valuable information about ENSO to the nation and world through observations, research, and forecasting.

Data corresponding to observed climate conditions are collected through the use of sophisticated weather instrumentation. One project, TOGA-TAO, was developed in response to the need for real-time data from the tropical Pacific. NOAA's Pacific Marine Environmental Laboratory and its partners developed this low-cost deep ocean mooring system to measure meteorological and oceanic conditions and transmit all the data to shore in real-time via satellite.

Many aspects of the ENSO phenomenon are studied so that there can be a better understanding of its nature and causes. For example, researchers analyzing climate diagnostics focus on such topics as understanding and predicting variations in tropical sea surface temperatures (SSTs); understanding and predicting the global impact of ENSO including identifying the global patterns of seasonal weather extremes; and the probability of occurrence of these extremes; Scientists also have been able show how El Niños/La Niñas impact Atlantic basin hurricane activity through changes in the global atmospheric circulation.

NOAA research scientists are now taking their understanding of ENSO a step further by comparing comprehensive descriptions of these events from the observed record with those simulated by numerical prediction models, which are computer programs designed to represent physical processes that occur in nature via mathematical equations.

NOAA researchers continue to work with scientists from around the world to design and build an improved global system for (1) observing the tropical oceans, (2) predicting El Niño/La Niña and other climate phenomena, and (3) making routine climate predictions readily available for use in decision making and planning purposes.

Much of the research done by the NOAA research laboratories has been transitioned into useful prediction tools for long-range climate outlooks offered through NOAA's operational forecasting branch.


A wildfire consumes a forest

Some areas experience drought during El Niño and this dryness can contribute to large-scale burning by uncontrolled wildfires.


Flood water from El Nino conditions make roads like this impassable

It is believed that El Niño conditions suppress the development of tropical storms and hurricanes in the Atlantic, and that La Niña favors hurricane formation in the Atlantic.


An example of bleached coral

Abnormal ocean currents during El Niño bring warm waters eastward from the western Pacific and leave low tides in the western Pacific.  Both can cause the bleaching and death of corals, damaging the balance of these ecosystems.


This global map shows a strong El Nino in the tropical Pacific

Scientists study El Niño in the tropical Pacific Ocean because it is the most common and powerful predictor of seasonal climate change.

NOAA Research programs that study El Niño and La Niña

checkmarkNOAA Climate Program Office (CPO)
checkmarkAtlantic Oceanographic and Meteorological Laboratory (AOML)
checkmarkEarth System Research Laboratory (ESRL)
checkmarkGeophysical Fluid Dynamics Laboratory (GFDL)
checkmarkPacific Marine Environmental Laboratory (PMEL)



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