IMPACT OF ENSO ON INDIA

Disclaimer: Copyright infringement not intended.

Context

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

Details

• 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.

https://www.downtoearth.org.in/news/climate-change/enso-has-affected-various-parts-of-india-separately-in-recent-decades-says-new-report-here-is-how-91119