With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct?

Answer: (b) 2 only

The IOD is an Indian Ocean see-saw that can offset El Niño. Statement 1 wrongly puts one pole in the Pacific.

Statement by statement

1. ✗ WRONG — both ends are in the Indian Ocean The IOD compares the western Indian Ocean (Arabian Sea side) with the eastern Indian Ocean (south of Indonesia). The Pacific belongs to El Niño (ENSO), not the IOD.

2. ✓ CORRECT A positive IOD (warmer west) pushes moisture towards India and can cancel part of El Niño’s drying — as in 1997 and 2019, when India got normal or excess rain despite El Niño.

The idea

The Indian Ocean Dipole is a difference in sea-surface temperature between the western and eastern tropical Indian Ocean. That difference changes where air rises and rain clouds gather. It can strengthen or weaken the influence of Pacific conditions on Indian rainfall; no single ocean signal guarantees a good or bad monsoon.

Positive IOD develops → Western Indian Ocean is relatively warm → Eastern waters near Indonesia are relatively cool → Rising air and rain shift towards the western basin → Indian monsoon circulation can benefit → Some El Niño drying may be offset

Why the others are wrong

(a) Statement 1 puts one end of the dipole in the Pacific — wrong.

(c) Accepts the Pacific end in statement 1 — mixing up the IOD with El Niño, the Pacific phenomenon.

(d) Statement 2 is right — IOD can offset El Niño.

The trap

“Tropical Eastern Pacific” is slipped into statement 1 because El Niño lives there. The IOD is an Indian Ocean see-saw only.

Elimination technique

Both poles of an Indian Ocean Dipole must be in the Indian Ocean. The Pacific endpoint makes statement 1 false, removing (a) and (c). Statement 2 still needs a separate check.

Also know

ENSO combines Pacific ocean warming or cooling with an air-pressure change called the Southern Oscillation. IOD is a separate Indian Ocean pattern and can develop without El Niño. The Madden–Julian Oscillation is a moving pulse of tropical cloud and rain that can affect active and break periods within a season.