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El Niño and the Summer Monsoon: A Comprehensive UPSC Blog

Relevance for UPSC Examination

  • Prelims: Physical Geography (climatic phenomena), Indian Geography (monsoon patterns)

  • Mains (GS-I): Geographical features, changes in critical geographical features, impacts on flora and fauna, disaster management (drought, heatwaves)


El Niño, a natural climate phenomenon, has significant implications for India’s monsoon season. In this UPSC analysis, we will delve into the ongoing El Niño event, its effects, and the forecast for the Indian summer monsoon in 2024. Let’s explore the key aspects related to El Niño and its impact on India.

What’s the Ongoing News?

The 2023-24 El Niño, one of the five strongest on record, has peaked and is gradually weakening. This phenomenon significantly contributed to 2023 ending as the warmest year ever recorded globally. Now, let’s understand what El Niño is and how it affects India.

IMD has predicted harsher spells of heatwaves in the regions marked by darker shades of red. (Image Source: Indian Express)

What Is El Niño?

  • El Niño refers to the abnormal warming of sea surface waters in the equatorial Pacific Ocean.

  • It typically emerges during autumn-summer in the northern hemisphere, peaking during winter (October-February) and weakening in the subsequent summer.

  • El Niño episodes last between 9 and 12 months, occasionally extending up to two years consecutively.

El Niño and India: Impacts on Monsoon and Heat

  • Increased temperatures: El Niño leads to higher temperatures and large-scale dryness globally.

  • Disrupted rainfall patterns: It disrupts normal rainfall patterns, affecting regions like East Africa.

  • Indian context: El Niño results in drier conditions during the monsoon season (June to September) in India.

  • Southwest Monsoon: El Niño conditions often have an inverse relationship with the Indian summer monsoon (June-September). This can result in reduced rainfall and drought-like conditions across portions of India.

  • Summer Temperatures: El Niño events tend to exacerbate heatwaves in India, potentially leading to adverse effects on agriculture, water resources, and public health.

Image Source: Indian Express

Image Source: Indian Express

Peaking and Weakening of El Niño

Implications for India and the Southwest Monsoon

  • Historical context: India faced the strongest El Niño in 1997, but the monsoon remained normal.

  • 2023 El Niño: Expected to develop following a triple dip La Niña event (2020-22).

  • Threats posed by El Niño: Reduced monsoon rainfall affects agriculture, inflation, and overall economic health.

  • Positive Indian Ocean Dipole (IOD): Currently positive, it boosts rains and counters El Niño effects.

Indian Summer Monsoon Forecast for 2024

  • IMD prediction: The country is likely to receive 96% of the southwest monsoon from June to September.

  • Importance of monsoon: Vital for India’s economy, replenishing reservoirs, power generation, and drinking supply.

  • Drought impact: Even a one-percentage-point decline in monsoon rainfall can lead to below-normal monsoons.

Understanding Monsoon Terms

  • Long Period Average (LPA): The average rainfall over a specified period (usually 30 years).

  • Rainfall categories:

  1. Large excess: Rainfall significantly above normal.

  2. Excess: Rainfall above normal.

  3. Normal: Average rainfall.

  4. Deficient: Rainfall below normal.

  5. Large deficient: Severe rainfall deficit.

  • Onset of the monsoon: The arrival of monsoon winds over Kerala marks its onset.

  • ENSO Neutral: Conditions where neither El Niño nor La Niña are present.

  • La Niña: A cooling of Pacific SSTs, the opposite of El Niño. It can lead to an intensified Indian monsoon.

  • Oceanic Niño Index (ONI): NOAA's metric to measure El Niño intensity using SST deviations.

Factors Determining Monsoon Onset

  • Trade winds: During El Niño, trade winds weaken, affecting monsoon winds in the Indian Ocean.

  • Indian Ocean Dipole (IOD): Positive IOD boosts monsoon rains and counters El Niño effects.

IMD: Role and Objectives

  • India Meteorological Department (IMD): Responsible for weather forecasting, climate monitoring, and disaster management.

  • El Niño and La Niña: Not mirror images; they differ in length and strength.

  • Impact of El Niño: Varies across sectors and regions; affects weather, ecosystems, and economies.

El Niño and La Niña Events are not Mirror Images of Each Other. They Differ in Length and Strength-How?

El Niño vs La Niña: Asymmetry in the Dance of the Pacific

El Niño and La Niña, the warm and cool phases of the El Niño-Southern Oscillation (ENSO) cycle, are crucial for UPSC CSE aspirants to understand due to their impact on global weather patterns. While they represent opposite ends of a spectrum, they aren't perfect mirror images. Here's a breakdown of their key differences for your exam preparation:


  • El Niño: El Niño events tend to be longer in duration, typically lasting 9 to 12 months, but can sometimes stretch for years.

  • La Niña: La Niña events are generally shorter, averaging around 9 months.


  • El Niño: El Niño events exhibit more variability in strength. Some El Niño events are weak and cause minimal disruptions, while others can be quite strong, leading to significant weather extremes.

  • La Niña: La Niña events tend to be more consistent in strength. They are typically moderate, bringing cooler than average temperatures but with less dramatic impacts compared to strong El Niño events.

Possible Reasons for the Asymmetry:

  • Non-linear interactions: The complex interplay between the ocean and atmosphere in the Pacific can lead to non-linear responses. Small changes in the ocean can trigger a strong El Niño event, while larger changes may be needed to produce a comparably strong La Niña.

  • Oceanic "memory": The deep Pacific Ocean has a large heat capacity and can retain warmth for extended periods. This "memory" may contribute to the persistence of El Niño events.

How El Nino Impacts-Know Sector and Region Wise

El Niño, the warm phase of ENSO, disrupts global weather patterns, impacting various sectors and regions differently. Here's a breakdown for UPSC CSE:

I. Sectoral Impacts:


  • Dry Regions: El Niño often brings droughts to Southeast Asia, Australia, and parts of Africa, leading to crop failures and food insecurity.

  • Wet Regions: Conversely, El Niño can cause excessive rainfall and flooding in South America and the southern United States, damaging crops and infrastructure.

  • Water Resources:

  • Droughts can significantly strain water availability for irrigation, drinking, and hydropower generation.


  • El Niño can disrupt ocean currents and upwelling, impacting fish migration patterns and reducing fish stocks in some regions.


  • Droughts can lead to malnutrition and waterborne diseases. Heatwaves associated with El Niño can cause heat stress and exacerbate respiratory illnesses.

Disaster Management:

  • Increased frequency and intensity of floods, droughts, wildfires, and cyclones due to El Niño pose significant challenges for disaster management efforts.

II. Regional Impacts:


  • Southeast Asia and parts of India often experience droughts during El Niño, impacting agriculture and water resources.


  • El Niño is linked to drier-than-average conditions and increased bushfire risk in Australia.


  • Eastern and Southern Africa can experience droughts, while West Africa may see increased flooding.

South America:

  • The west coast of South America, especially Peru, experiences heavier rainfall and potential flooding during El Niño.

North America:

  • El Niño can lead to milder winters and drier conditions in Southern California, while the Pacific Northwest may experience increased precipitation.

Important Considerations for UPSC CSE:

  • The strength and duration of El Niño events significantly influence their impact.

  • Regional vulnerabilities play a crucial role. Areas with limited water resources or underdeveloped infrastructure are more susceptible to El Niño's effects.

  • El Niño interacts with other climate phenomena, making it challenging to predict its precise impacts.


  • Focus on linking El Niño to specific challenges faced by India, like droughts, floods, and food security.

  • Discuss relevant government initiatives like drought mitigation programs or disaster preparedness measures.

  • Highlight the importance of international cooperation for monitoring ENSO and mitigating its effects.

By demonstrating a nuanced understanding of El Niño's sectoral and regional impacts, you can strengthen your UPSC CSE preparation and showcase your ability to address climate-related issues.

The Intertropical Convergence Zone (ITCZ):

The Intertropical Convergence Zone (ITCZ) is a band of low pressure circling the Earth near the equator. Understanding the ITCZ is vital for UPSC CSE due to its significant influence on global weather patterns and regional climates, particularly in India.

What is the ITCZ?

  • The ITCZ is where trade winds from the Northern and Southern Hemispheres converge.

  • Intense solar radiation heats the air and water in this zone, creating a region of rising air currents.

  • As the air rises, it cools and condenses, leading to frequent thunderstorms and heavy rainfall.

Significance for UPSC CSE:

  • Monsoons: The seasonal migration of the ITCZ is a key driver of monsoons in India. During summer, the ITCZ shifts northward, bringing heavy rainfall to the Indian subcontinent.

  • Climate and Agriculture: The ITCZ's position and intensity significantly influence regional rainfall patterns, impacting agricultural productivity and food security. Deviations from normal ITCZ patterns can lead to droughts or floods, posing significant challenges for India.

  • Disaster Management: The ITCZ's influence on monsoons and extreme weather events necessitates effective disaster management strategies for floods, landslides, and cyclones.

Exam-oriented Focus:

  • Explain the link between the ITCZ's movement and the Indian monsoon system.

  • Discuss the socio-economic implications of variations in ITCZ activity, including impacts on agriculture, water resources, and disaster management.

  • Mention technological advancements like remote sensing for monitoring the ITCZ and its impact on weather forecasting.

Additional Points to Consider:

  • The ITCZ's position is not static. It migrates seasonally, following the path of the overhead sun.

  • The ITCZ's impact can be amplified by climate change, potentially leading to more extreme weather events.

By understanding the ITCZ and its connection to Indian weather patterns, you can effectively address climate-related issues relevant to the UPSC CSE syllabus. Focus on highlighting its role in monsoons, agriculture, and disaster management to showcase your grasp of this crucial concept.

Recommended Resources:


Understanding El Niño and its implications is crucial for UPSC aspirants. As India prepares for the 2024 monsoon season, the interplay of El Niño, IOD, and other factors will shape our nation’s climate and economy.

Remember, knowledge of El Niño and its effects is essential for any serious UPSC candidate. Stay informed and keep learning!

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