The Indian monsoon, driven by complex ocean-atmosphere interactions, is highly sensitive to global climatic phenomena, particularly El Niño. El Niño is the warm phase of the El Niño-Southern Oscillation (ENSO) cycle, originating in the equatorial Pacific Ocean but profoundly influencing Indian monsoon rainfall patterns through teleconnections. In most El Niño years, India experiences deficient rainfall, droughts, and altered weather patterns, impacting agriculture, water availability, and the economy.
What is El Niño?
El Niño is caused by anomalous warming of sea surface temperatures (SSTs) in the central and eastern equatorial Pacific Ocean, disrupting global circulation patterns. For classification, SST anomalies must be ≥0.5°C above normal in the Nino 3.4 region for three consecutive months.
Formation Process
- Weakening/reversal of trade winds
- Eastward spread of warm waters toward South America
- Shift of convection from the Indian Ocean to the central Pacific, reducing monsoon rainfall over India
Key Characteristics
- Warm central/eastern Pacific SSTs
- Weak or reversed Walker Circulation
- Reduced convection over the Indian Ocean
- Weaker monsoon and drought risks in India
ENSO Cycle and Monsoon
- El Niño (warm phase): Weak monsoon, below-normal rainfall (e.g., 2009 → 22% deficit)
- La Niña (cold phase): Stronger monsoon, excess rainfall (e.g., 2010 floods)
- ENSO-neutral: Normal rainfall (e.g., 2017 → ~98% of LPA)
Walker Circulation and SOI
The Walker Circulation, normally driving monsoon winds, weakens or reverses during El Niño, suppressing rainfall. The Southern Oscillation Index (SOI), based on pressure differences between Tahiti and Darwin, is a key predictor:
- SOI < -8 → El Niño, weak monsoon
- SOI > +8 → La Niña, strong monsoon
Impacts on Indian Monsoon
Suppression of Monsoon Circulation
- Weak Bay of Bengal low-pressure system → reduced winds and rainfall
- Northward shift of monsoon trough → rainfall concentrated in Himalayan foothills, drought in central/western India
- Increased western disturbances → erratic rainfall, hailstorms
- Delayed onset and early withdrawal → shortened rainy season
Historical Trends
- 1982, 1987, 2002, 2009, 2015 → severe droughts with rainfall deficits of 14–22%
- 1997, 2023 → weak impact due to strong positive IOD
Other Climate Drivers
Indian Ocean Dipole (IOD)
- Positive IOD: Enhances rainfall, offsets El Niño (e.g., 1997, 2019)
- Negative IOD: Weakens monsoon, worsens El Niño impact
Madden-Julian Oscillation (MJO)
- Phases 2–3 (Indian Ocean) → strengthen monsoon
- Phases 6–7 (Pacific) → suppress monsoon
- Strong MJO can temporarily mitigate El Niño effects
Economic and Agricultural Impact
Agriculture
- Rainfed crops (pulses, oilseeds, millets, cotton) worst affected
- Kharif crops like rice and maize see delayed sowing and reduced yields
- Example: 2015 El Niño reduced pulses and oilseeds output by 15%
Food Inflation
- Supply shortages lead to food price spikes
- 2009 El Niño drought → food inflation peaked at 19%
Water & Energy
- Lower reservoir storage → scarcity in Maharashtra, Karnataka, Gujarat, Tamil Nadu
- Hydropower generation drops by up to 20% during strong El Niño years
2023–24 El Niño Event
- Peaked in Dec 2023, weakened by mid-2024
- Monsoon deficit only ~6% (milder due to positive IOD)
- Impacts: 8% drop in kharif crop output, 30–40% rise in food prices, water shortages in reservoirs
- Government response: MSP hikes, PM-KISAN cash transfers, export bans on rice/onions, AI-based forecasting
Government Measures
Agricultural Adaptation
- Promotion of drought-resistant crops (millets, pulses)
- Expanded irrigation schemes (PMKSY, micro-irrigation)
- Crop insurance via PMFBY
Water and Food Security
- Jal Shakti Abhiyan for water harvesting and recharge
- Buffer food stockpiles for inflation control
- AI + ISRO satellite-based monsoon forecasting
Disaster Preparedness
- Strengthening NDRF and state drought relief systems
- Price stabilization measures to control inflation
Conclusion
El Niño significantly disrupts the Indian monsoon by weakening circulation, delaying onset, and reducing rainfall. While strong El Niño years have historically led to severe droughts, the role of IOD and MJO can alter impacts. The 2023–24 event showed a milder effect due to a positive IOD, but still caused agricultural and economic stress. Effective forecasting, crop diversification, water conservation, and policy interventions remain crucial to mitigating El Niño’s adverse impacts on India’s agriculture, economy, and livelihoods.