El Niño, La Niña and the Indian Monsoon

A patch of unusually warm water off Peru’s coast can decide whether Indian farmers see a good harvest. That link runs through a single climate pattern: ENSO.

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Indian Geography · IndGeo0054

ENSO: The Pacific Swing That Shapes the Monsoon

El Niño (warm)

• Pacific off Peru warms up
• Weakens easterly trade winds
• Generally suppresses monsoon rainfall

La Niña (cool)

• Pacific off Peru cools down
• Strengthens easterly trade winds
• Generally boosts monsoon rainfall

16 / 7

El Niño years since 1950 / how many turned out below-normal

2002 & 2009

Two of India’s worst El Niño-linked droughts

Not a guaranteed signal

Less than half of India’s El Niño years actually brought a below-normal monsoon — which is exactly why the IMD also watches the Indian Ocean Dipole before making a call.

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Must Know

• ENSO, the El Niño-Southern Oscillation, is a recurring shift in sea-surface temperatures and winds across the tropical Pacific Ocean.
• ENSO swings irregularly between three phases: El Niño (warm), La Niña (cool), and Neutral, roughly every two to seven years.
• El Niño occurs when the central and eastern Pacific, off Peru, warms up more than usual.
• La Niña occurs when that same region cools down more than usual.
• ENSO’s phase strongly influences how India’s southwest monsoon behaves each year.

Good to Know

• El Niño warming weakens the easterly trade winds that normally carry moisture toward India. This generally suppresses monsoon rainfall.
• La Niña cooling strengthens those same easterly winds. This generally boosts monsoon rainfall above normal.
• But the link isn’t automatic. Since 1950, India has had 16 El Niño years. Only 7 of those saw below-normal monsoon rainfall.
• This mixed record is why forecasters also track other factors, like the Indian Ocean Dipole (IOD). El Niño alone is not read as a guaranteed bad-monsoon signal.

Test Yourself

Please wait…

1. El Niño occurs when the ocean off which country’s coast warms more than usual?

India

Australia

Peru

South Africa

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Great to Know

• Several of India’s worst droughts since independence coincided with El Niño years, including 1972, 2002, and 2009.
• The 2002 drought was especially severe. It brought a 19% rainfall deficit, hit 29% of the country, and cost about 24 million tonnes of food grain.
• The 2009 drought was the third-worst since 1901, with a 23% rainfall deficit affecting roughly 59% of the country’s area.
• The India Meteorological Department (IMD) tracks ENSO’s status closely when forecasting each year’s monsoon. It issues ENSO-linked updates and rainfall forecasts throughout the season. ENSO’s state is one of the strongest single predictors available for the monsoon’s overall strength.