Key Terms & Concepts — UPSC Mains
Indian Ocean Dipole
"An east-west seesaw in sea surface temperatures across the tropical Indian Ocean that strongly influences the Indian monsoon"
The Indian Ocean Dipole (IOD), sometimes called the Indian Nino, is a climate phenomenon defined by the difference in sea surface temperatures between the western tropical Indian Ocean (near the Arabian Sea) and the eastern tropical Indian Ocean (near Indonesia). In a positive IOD the west is warmer than the east, which generally strengthens the Indian southwest monsoon; in a negative IOD the pattern reverses and tends to weaken it. The IOD interacts with El Nino and La Nina in the Pacific to shape the strength and distribution of India's monsoon rainfall.
Relevant for GS1 (geography, climatology, monsoon dynamics). Understanding the IOD is essential to interpreting India's seasonal rainfall forecasts, which affect agriculture, water and the economy. For 2026, the IMD noted neutral IOD conditions with a positive IOD likely late in the season, against a strong El Nino, part of its below-normal monsoon forecast of about 90% of the long-period average.
- 1 The IOD measures the sea surface temperature difference between the western and eastern tropical Indian Ocean
- 2 Positive IOD (warmer west) generally aids the Indian southwest monsoon
- 3 Negative IOD (warmer east) generally suppresses monsoon rainfall
- 4 Works together with El Nino and La Nina in the Pacific to modulate the monsoon
- 5 A positive IOD can partly offset the drying effect of an El Nino
- 6 Also influences rainfall and droughts in East Africa, Indonesia and Australia
- 7 IMD monitored neutral IOD conditions in 2026, expecting a positive IOD late in the monsoon
For the 2026 monsoon the IMD reported neutral Indian Ocean Dipole conditions with a positive IOD likely to develop late in the season, one factor in its below-normal forecast of about 90% of the long-period average amid a strong El Nino.
