Why the Indian Ocean Dipole is in the News | Explained

A woman walks along the boardwalk on a rainy monsoon day at Marine Drive in Mumbai. File | Photo credit: PTI

In the monsoon of 1997, the central Pacific was ruled by one of the most severe heat waves in its recorded history in the form of an El Niño so violent that, by all accounts, India should have been staring at one of its worst droughts. But in the biggest of meteorological surprises, monsoon rainfall from June to September ended up being in excess, about 2% above normal. India Meteorological Department (IMD) Director General Mrutyunjay Mohapatra notes that “this has only happened once”. The agent of that escape was sitting not in the Pacific, but in the Indian Ocean in the backyard, and it’s called the Indian Ocean Dipole (IOD). With a “Super El Niño” forecasts for this year, it is an open meteorological question whether the situation of 1997 could be repeated. India’s monsoon is currently 40% deficient, with the IMD expecting June to September to see 90% – slightly more than a “deficit” – of the long-term average.

The equatorial oceans and the air directly above them are two layers in endless conversation, forever trading moisture. Where the sea surface is warm, water vapor breathes upward; moist air rises, cools, condenses into clouds, and falls back as rain. Where the surface is cold, air descends and the sky lingers. Pacific runs the largest version of this engine. The trade winds pull water warmed by the sun and accumulate it near Indonesia, where air rises in heavy rain, drifts aloft back east, and sinks over the cool eastern Pacific off South America.

Published – 01 Jul 2026 10:38 IST