La Niña and El Niño Modoki
Geography › El Niño and Climate Classification · Topic 9.3
La Niña is the cool phase of ENSO, in which stronger trade winds and more upwelling make the eastern and central equatorial Pacific colder than normal, usually bringing a good Indian monsoon. El Niño Modoki, or the central Pacific El Niño, is a variety with warming in the central Pacific and cooler water on both sides. The Indian Ocean Dipole is a separate temperature see-saw that also affects the monsoon.
6 min read · UPSC Prelims · Geography · El Niño and Climate Classification
At a Glance
- La Niña Cold central and eastern Pacific; strong trades
- Threshold Niño 3.4 at minus 0.5 degrees Celsius or lower
- El Niño Modoki Warm central Pacific, cool east and west
- Positive IOD Warm west Indian Ocean; good monsoon
- Negative IOD Warm east Indian Ocean; weaker monsoon
- Exam link UPSC Prelims, Geography: El Niño and Climate Classification
Where Does It Fit?
This is the third topic of the category on El Niño and climate classification. The previous topic described El Niño, and this one covers its opposite, La Niña, its variant, Modoki, and the Indian Ocean Dipole. The next topic begins climate classification with the Köppen scheme. Previous topic: El Niño and Its Effects. Next topic: Köppen Scheme of Climate Classification.
What Is La Niña?
In short: La Niña is an exaggeration of normal conditions: stronger trade winds and a colder eastern Pacific.
La Niña, Spanish for the little girl, is the cool phase of the El Niño-Southern Oscillation, and is sometimes called El Viejo or the anti-El Niño. The trade winds blow stronger than normal, pushing more warm water into the western Pacific, and upwelling of cold water off South America is enhanced. The sea surface in the central and eastern equatorial Pacific is below normal, and the Niño 3.4 anomaly stays at or below minus 0.5 degrees Celsius. The pressure is higher than normal at Tahiti and lower at Darwin, so the Southern Oscillation Index is strongly positive, as in Walker Circulation and Normal Conditions in the Pacific. When the Pacific is close to normal, with neither El Niño nor La Niña, the state is called ENSO-neutral. La Niña usually occurs after an El Niño, though not always, and may last for one or two years: the triple-dip La Niña of 2020 to 2023 lasted for three northern winters.
| Region | Typical La Niña effect |
|---|---|
| India | Generally a good or normal monsoon; colder winters with more severe cold waves in the north in some years |
| Indonesia and Australia | Heavy rain and floods, as in eastern Australia in 2021 and 2022 |
| Peru and Ecuador | Cooler and drier; richer fisheries |
| Southern United States | Drier winters and droughts |
| Atlantic | More active hurricane season |
| Global | Slightly lower global average temperature than in an El Niño year |
What Is El Niño Modoki?
El Niño Modoki is a type of El Niño, described by researchers in the 2000s, including Karumuri Ashok and Toshio Yamagata, in which the strongest warming is in the central Pacific, with cooler water on both its east and west. The word Modoki is Japanese for similar but different. It is also known as the Central Pacific El Niño or the dateline El Niño, in contrast to the conventional or eastern Pacific El Niño with warming near the South American coast. In a Modoki, there are two Walker cells, with rising air over the central Pacific and sinking air to both the east and west, as in the Walker Circulation. The western branch can bring sinking air over the Indian Ocean region. The impacts differ: Peru is not flooded as in a classical El Niño, but the effects on the monsoon, on Australian rainfall and on the winters of the United States can be different or even stronger. Researchers have linked the Modoki to some Indian monsoon deficits. Such events have become more common in recent decades, and whether this is due to warming is still being studied.
What Is the Indian Ocean Dipole?
The Indian Ocean Dipole, IOD, is an irregular see-saw in sea surface temperature between the western Indian Ocean, near Africa, and the eastern Indian Ocean, near Sumatra. It was described by Saji and colleagues in 1999, and is measured by the Dipole Mode Index, which is the temperature difference between the two regions.
| Phase | Sea surface temperature | Effect |
|---|---|---|
| Positive IOD | Western Indian Ocean warmer; eastern cooler, with upwelling off Sumatra | More rain over East Africa and over India, with a stronger monsoon; drought in Indonesia and southern Australia |
| Negative IOD | Western Indian Ocean cooler; eastern warmer | More rain over Indonesia and Australia; weaker rainfall over East Africa and India |
The dipole can work with or against ENSO. In 1997, a positive IOD offset the effect of the strong El Niño, so that the Indian monsoon was normal. In 2019, a very strong positive IOD helped the monsoon to end at about 110 per cent of the average, although the Pacific was close to neutral, and it also contributed to the severe bushfires of Australia that year, as in El Niño and Its Effects. As an analytical point, the Indian monsoon is thus the product of multiple oceans, and good forecasting needs the Pacific, the Indian Ocean and the land together, as in Mechanism of the Indian Monsoon.
Why Is This Topic Important?
- Asked together Phases and effects
- Forecasting Monsoon prediction
- Current affairs Modoki and IOD in news
What Came Next?
The next topic begins the study of climate classification with the Köppen scheme. Next topic: Köppen Scheme of Climate Classification.
Key People and Terms
- La Niña Cool phase of ENSO
- ENSO-neutral Neither El Niño nor La Niña
- El Niño Modoki Central Pacific El Niño
- Indian Ocean Dipole West-east temperature see-saw
- Dipole Mode Index Measure of the IOD
- Triple-dip La Niña lasting three winters
Exam Corner
Points to Remember
- La Niña is cold in the east Pacific; trades are stronger.
- La Niña usually brings a good monsoon.
- Modoki means similar but different.
- Positive IOD helps the monsoon.
- 1997 and 2019 were IOD examples.
Do Not Confuse With
- La Niña and neutral Cold phase versus normal
- Modoki and canonical El Niño Central versus eastern Pacific warming
- IOD and ENSO Indian Ocean versus Pacific
Memory Hook
La Niña: cold east, strong trades, rain for India; Modoki: warm middle; IOD: positive is kind.
Mains Angle
Questions ask about ocean links to the monsoon. These points add depth.
- Phases La Niña, Modoki, IOD
- Interaction IOD can offset ENSO
- Forecast Multi-ocean models
A Question You May Face
An original practice question, not a past paper question.
“Explain La Niña, El Niño Modoki and the Indian Ocean Dipole and their combined influence on the Indian monsoon.”
How to Answer
- La Niña Cold phase and effects.
- Modoki Central warming.
- IOD Positive and negative.
- Combination 1997 and 2019.
GS Relevance
Frequently Asked Questions
What is La Niña?
La Niña is the cool phase of the El Niño-Southern Oscillation, in which the trade winds strengthen and the sea surface of the central and eastern equatorial Pacific becomes colder than normal. It often brings a good Indian monsoon, floods in Australia and Indonesia, and droughts in the southern United States.
What is the difference between El Niño and La Niña?
El Niño is a warm phase with weak trade winds, a warm eastern Pacific and a negative Southern Oscillation Index, which often reduces Indian rainfall. La Niña is a cold phase with strong trade winds, a cold eastern Pacific and a positive index, which often increases Indian rainfall.
What is El Niño Modoki?
El Niño Modoki, also called the central Pacific El Niño, is a type of El Niño where the warmest water is in the central Pacific, with cooler water to the east and west. The word Modoki is Japanese for similar but different, and its climatic effects differ from the conventional El Niño.
What is the Indian Ocean Dipole?
The Indian Ocean Dipole is a see-saw in sea surface temperature between the western and eastern Indian Ocean. In its positive phase the west is warmer and the east cooler, which usually strengthens the Indian monsoon; in the negative phase, the pattern reverses and the monsoon tends to weaken.
How can the Indian Ocean Dipole offset El Niño?
A positive Indian Ocean Dipole warms the western Indian Ocean and increases moisture and rain-bearing winds over India, which can compensate for the drying effect of El Niño. In 1997, a strong positive dipole kept the Indian monsoon normal despite a very strong El Niño.
PYQ Practice — Statement Analysis
1 La Niña is associated with stronger trade winds across the Pacific.
More cold water upwells in the east.
2 A positive Indian Ocean Dipole generally weakens the Indian monsoon.
It generally strengthens it.
3 El Niño Modoki has its strongest warming in the central Pacific.
The east and west are cooler.
4 La Niña is the warm phase of ENSO.
It is the cool phase.
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