Examine the relationship between El Niño and the Indian southwest monsoon. How does the Indian Ocean Dipole modulate this relationship? Discuss with recent examples.

Q. Examine the relationship between El Niño and the Indian southwest monsoon. How does the Indian Ocean Dipole modulate this relationship? (15 marks, 250-350 words)

The southwest monsoon (June–September) delivers about three-fourths of India's rainfall, and its interannual variability is governed largely by Pacific and Indian Ocean sea-surface temperatures. El Niño — abnormal warming of the central-eastern Pacific — is the single strongest predictor of a weak monsoon, but the link is probabilistic, not deterministic, and is significantly modulated by the Indian Ocean Dipole (IOD).

How El Niño weakens the monsoon - Displaced Walker circulation: Pacific warming shifts convection eastward, leaving descending, drier air over the Indian subcontinent and weakening moisture-laden cross-equatorial winds. - Weakened land–sea thermal contrast suppresses the monsoon trough and lengthens intra-seasonal break spells. - Forecast evidence: with El Niño developing in 2026, IMD lowered its seasonal forecast to 90% of LPA (±4%), assigning an 84% probability to below-normal or worse rainfall [1][2]. - Not deterministic: roughly four in ten El Niño years still record normal rainfall, so IMD treats ENSO as one predictor among several in the MMCFS model built under the National Monsoon Mission [3][4].

How the IOD modulates the relationship - A positive IOD (warmer western Indian Ocean) draws convection towards the Arabian Sea, strengthening moisture supply and partly offsetting El Niño's drying. - A negative IOD compounds El Niño; a neutral IOD offers no buffer — the situation in 2026, when IMD projected neutral conditions alongside a developing El Niño [1]. - Recent examples: the strong 1997–98 El Niño still yielded above-normal Indian rainfall because a strongly positive IOD countered it — a rare exception; by contrast, 2026 saw a below-normal seasonal outlook and a below-normal July forecast with no IOD cushion [1][4].

Thus El Niño loads the dice against a good monsoon, while the IOD decides how heavily. Strengthening coupled ocean–atmosphere modelling, expanding Indian Ocean observation networks, and linking forecasts to contingency crop planning and reservoir management would convert probabilistic warnings into resilience — advancing food security and SDG-13 on climate action.

(~310 words)

Sources: 1. Updated Long Range Forecast for the Southwest Monsoon Seasonal Rainfall during June–September 2026, PIB/IMD — 90% of LPA forecast, El Niño development, neutral IOD, below-normal monthly outlook 2. Long Range Forecast for the 2026 Southwest Monsoon Season Rainfall, PIB/IMD — 84% probability of below-normal or less rainfall 3. PIB Press Note: The Indian Monsoon — MMCFS and National Monsoon Mission forecasting framework 4. Earth Sciences Minister explains El Niño and its monsoon impact, Lok Sabha reply, PIB — probabilistic nature of the El Niño–monsoon link and historical exceptions