IAS Gyan

Daily News Analysis


11th August, 2023 Geography

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The complex interplay between the El Nino Southern Oscillation (ENSO), global warming, and their impact on monsoon rainfall patterns in different regions of India.


  • The El Nino Southern Oscillation (ENSO) is a climate phenomenon characterized by sea surface temperature changes in the equatorial Pacific Ocean.
  • ENSO affects monsoon rainfall patterns in India, with varying impacts across different regions.
  • El Nino (warming phase) suppresses monsoon rainfall, while La Nina (cooling phase) enhances it.

Recent Research Findings

  • A research paper published in Nature Scientific Reports in August 2023 reveals the changing impact of ENSO on India's monsoon rainfall.
  • The impact varies across regions: greater in northern, lesser in central, and relatively constant in southern India.
  • Global warming contributes to this phenomenon.

El Nino and Monsoon Suppression

  • El Nino causes subsidence of air, suppressing monsoon rainfall.
  • ENSO-related events were announced by World Meteorological Organization (WMO) and India Meteorological Department (IMD).
  • A recent La Nina phenomenon ended in March 2023.

Local Factors in Monsoon Rainfall

  • Monsoon rainfall is influenced by ENSO and local factors like monsoon trough strength and frequency of low-pressure areas.
  • Monsoon depressions play a crucial role in causing rainfall during the monsoons.

Changing ENSO Impact

  • Analysis of data from 1901 to 2018 reveals evolving trends.
  • Strength of monsoon trough and low-pressure areas declining across India.
  • El Nino forming later in the year, impacting monsoon rainfall delay.

Compensation Effect and Weakening Relationship

  • Warming of the Arabian Sea due to global warming sends moisture to central India.
  • The compensation is leading to a weakening of the relationship between monsoon rainfall over central India and El Nino.

Shift in Monsoon Depressions

  • Monsoon depressions moving southward in recent decades.
  • This has reduced their influence over northern India and has increased the influence of El Nino on the region.
  • Southward movement reasons were currently unknown.

Historical Trends and Uncertain Future

  • The relationship between ENSO and monsoon rainfall strengthens till 1940, remains stable till 1980, and weakens thereafter.
  • Future changes are uncertain due to evolving ENSO patterns and global warming effects.

Incorporating Differential Impact for Improved Forecasting

  • There is a need to incorporate varying El Nino impact into climate models for better regional rainfall forecasts.
  • There is a shifting of the ENSO onset region from the extreme eastern Pacific to the east-central Pacific Ocean.
  • The differential impact of El Nino has to be incorporated into climate modelling for accurate regional forecasts during ENSO events.

About El Nino Southern Oscillation

  • El Nino Southern Oscillation (ENSO) is a complex and recurring climate phenomenon that involves interactions between the ocean and the atmosphere.
  • It has significant impacts on weather patterns, sea surface temperatures, and ecosystems across the globe, particularly in the Pacific Ocean region and beyond.

Key Components of ENSO

El Nino Phase: Warm Anomaly

  • El Nino refers to the warming of sea surface temperatures in the central and eastern equatorial Pacific Ocean.
  • This phase disrupts the normal atmospheric circulation patterns, leading to far-reaching effects on global climate.
  • Warmer waters in the Pacific lead to changes in wind patterns, rainfall distribution, and ocean currents.

La Nina Phase: Cool Anomaly

  • La Nina is the opposite phase of ENSO, characterized by cooler-than-average sea surface temperatures in the central and eastern equatorial Pacific.
  • It triggers distinct atmospheric patterns, including increased trade winds and upwelling of cold oceanic waters along the coasts of South America.

ENSO Cycle

  • The ENSO cycle typically oscillates between El Nino and La Nina phases every 2 to 7 years, although the intervals can vary.
  • The transitions between these phases are often associated with shifts in atmospheric pressure systems, wind patterns, and oceanic circulation.

Impacts of ENSO

Global Weather Patterns

  • ENSO influences weather patterns worldwide, affecting regions far from the Pacific Ocean.
  • El Nino can lead to droughts, heatwaves, and reduced rainfall in some areas, while causing heavy rains, flooding, and increased cyclone activity in others.
  • La Nina, on the other hand, can result in increased rainfall, cooler temperatures, and heightened hurricane activity.

Agriculture and Food Security

  • ENSO-induced droughts or excessive rainfall can impact crop yields, leading to agricultural losses and affecting food production.
  • Crop failures and disrupted growing seasons can threaten food security in affected regions.

Economic and Environmental Consequences

  • ENSO-related weather extremes can lead to economic losses due to damaged infrastructure, reduced agricultural output, and increased disaster management costs.
  • Ecosystems, fisheries, and marine life can also be disrupted by changes in ocean temperatures and currents.

Prediction and Monitoring

  • Scientists and meteorological agencies closely monitor ENSO indicators, such as sea surface temperatures and atmospheric pressure patterns, to predict its phases.
  • Advanced forecasting models help anticipate potential impacts on weather and climate, allowing for preparedness and mitigation efforts.


Q) Discuss the significance of El Nino Southern Oscillation (ENSO) in the context of global climate dynamics and its impact on weather patterns, agriculture, economies, and ecosystems across different regions.