El Niño

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How strong El Niño conditions develop

Map of the tropical Pacific Ocean highlighting the four ENSO (El Niño-Southern Oscillation) regions: Niño 4, Niño 3.4, Niño 3, and Niño 1+2. The regions are marked as colored rectangles along the equator from near Australia to the coast of South America, illustrating key zones used to monitor El Niño and La Niña climate events.

Diagram of the equatorial Pacific Ocean showing El Nino conditions, with weak trade winds, increased rainfall over South America, increased convection, a deepened thermocline, and suppressed upwelling.

Two diagrams compare coastal upwelling during normal conditions and an El Nino event. The top shows strong upwelling with nutrient-rich water and high plankton near the coast, while the bottom shows weak upwelling, a thicker nutrient-poor surface layer, and reduced plankton during El Nino.

World map illustrating the generalized weather effects of El Nino from December through February. Regions are labeled and shaded to show conditions such as warm in parts of North America, Asia, and South America; wet in the southern United States and eastern South America; dry and warm in southern Africa and Southeast Asia; wet and cool in the northern United States; and wet and warm across central and eastern equatorial Pacific.

Images of sea-surface height taken during the El Nino episodes of 1997 and 2015.

Graph depicting the influence of El Niño/Southern Oscillation (ENSO) on rainfall produced by the Indian summer monsoon. During years when ENSO is active, monsoon-driven precipitation over India often declines.

At a Glance

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El Niño summary

El Niño: Media

oceanic and climatic phenomenon

Images

How strong El Niño conditions develop

How strong El Niño conditions develop

A map explaining how an El Niño episode develops in the Pacific Ocean and what effects...

Encyclopædia Britannica, Inc.

Map of the tropical Pacific Ocean highlighting the four ENSO (El Niño-Southern Oscillation) regions: Niño 4, Niño 3.4, Niño 3, and Niño 1+2. The regions are marked as colored rectangles along the equator from near Australia to the coast of South America, illustrating key zones used to monitor El Niño and La Niña climate events.

Monitoring regions for the El Niño-Southern Oscillation (ENSO)

The important part of the equatorial Pacific Ocean is the Niño 3.4 region. The temperature...

Encyclopædia Britannica, Inc.

Two diagrams compare coastal upwelling during normal conditions and an El Nino event. The top shows strong upwelling with nutrient-rich water and high plankton near the coast, while the bottom shows weak upwelling, a thicker nutrient-poor surface layer, and reduced plankton during El Nino.

Upwelling process along coast

The upwelling process in the ocean along the coast of Peru. A thermocline and a nutricline...

Encyclopædia Britannica, Inc.

World map illustrating the generalized weather effects of El Nino from December through February. Regions are labeled and shaded to show conditions such as warm in parts of North America, Asia, and South America; wet in the southern United States and eastern South America; dry and warm in southern Africa and Southeast Asia; wet and cool in the northern United States; and wet and warm across central and eastern equatorial Pacific.

El Niño is associated with substantial changes to established weather patterns between December and February

The weather effects of El Niño include pronounced drought episodes in the western...

Encyclopædia Britannica, Inc.

Images of sea-surface height taken during the El Nino episodes of 1997 and 2015.

Images of sea-surface height taken during the El Niño episodes of 1997 and 2015, which help to compare the intensity and extent of warm water in the eastern tropical Pacific Ocean

El Niño episodes are characterized by unusually warm ocean conditions along the tropical...

NASA

Graph depicting the influence of El Niño/Southern Oscillation (ENSO) on rainfall produced by the Indian summer monsoon. During years when ENSO is active, monsoon-driven precipitation over India often declines.

Graph depicting the influence of El Niño/Southern Oscillation (ENSO) on rainfall...

Encyclopædia Britannica, Inc.

Interactives

Diagram of the equatorial Pacific Ocean showing El Nino conditions, with weak trade winds, increased rainfall over South America, increased convection, a deepened thermocline, and suppressed upwelling.

Comparing El Niño, La Niña, and neutral ENSO conditions

Use this interactive diagram to explore how shifts in trade winds and sea surface...

Encyclopædia Britannica, Inc.

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