Indian Ocean Dipole
In one line: The Indian Ocean Dipole (IOD) is the difference in sea surface temperature between the western and eastern parts of the tropical Indian Ocean.
The two phases
In a positive IOD, the western Indian Ocean (near Africa) is warmer than the eastern part (near Indonesia). This tends to favour convection and rain over India. In a negative IOD the pattern reverses and tends to reduce Indian rain.
Why forecasters watch it
The IOD can modify El Niño's effect. A positive IOD can partly offset the drying effect of El Niño, which is why some El Niño years still see near-normal monsoons. UPSC asked about exactly this link in Prelims 2017.
Why it is in the news
With El Niño strengthening in 2026, forecasters tracked the IOD for any offsetting effect; the season still ended deficient.
Where to go next
- El Niño and the Indian monsoon
- Northeast monsoon
Indian Ocean Dipole in the news
- Monsoon 2026 ends 12.6% below normal, India's weakest season since 2015 1 October 2026
The Indian Ocean pattern that can soften an El Niño.
- El Niño, heat deaths and why parched Maharashtra cannot declare drought yet 24 September 2026
The monsoon's regional counterweight
- India records its hottest August since 1901; IMD forecasts below-normal September rain 1 September 2026
The Indian Ocean's own see-saw
Previous-year questions on this
- 2017 · GS1 · 15 marks What characteristics can be assigned to monsoon climate that succeeds in feeding more than 50 percent of the world population residing in Monsoon Asia?
- 2015 · GS1 · 12.5 marks How far do you agree that the behaviour of the Indian monsoon has been changing due to humanising landscape? Discuss.
- 2014 · GS3 · 12.5 marks Drought has been recognised as a disaster in view of its spatial expanse, temporal duration, slow onset and lasting effect on various vulnerable sections. With a focus on the September 2010…
- 2014 · GS1 · 10 marks Most of the unusual climatic happenings are explained as an outcome of the El-Nino effect. Do you agree?
- 2017 · Prelims With reference to 'Indian Ocean Dipole (IOD)' sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct? 1. IOD phenomenon is characterised…