Context
A Positive Indian Ocean Dipole (IOD) or Indian Nino is set to re-emerge for the second consecutive year in the latter half of 2024, marking the first time this event has occurred back-to-back since 1960.
About Indian Ocean Dipole
IOD is a climate phenomenon in the Indian Ocean, similar to El Niño and La Niña in the Pacific Ocean.
It refers to the difference in sea surface temperatures (SST) between the western (near Somalia) and eastern (near Indonesia and Malaysia) parts of the Indian Ocean.
Positive IOD: Cooler SST in the east and warmer SST in the west.
Negative IOD: Warmer SST in the east and cooler SST in the west.
Positive IOD often coincides with El Niño, while Negative IOD is sometimes linked to La Niña.
Mechanism
Normal Year: Warm waters from the western Pacific move into the Indian Ocean, slightly warming it, promoting rising air and enhanced air circulation.
Negative IOD: Intensified circulation pushes warm water from the African coast towards Indonesia, warming the eastern Indian Ocean.
Positive IOD: Warmer waters in the west and cooler waters in the east shift winds, bringing more rainfall to Eastern Africa and the Indian subcontinent, while Southeast Asia, Indonesia, and Australia receive less rainfall.
Impact on Global Weather Patterns
Positive IOD: Increases rainfall in Eastern Africa and the Indian subcontinent, but suppresses rainfall in Indonesia, Southeast Asia, and Australia.
Negative IOD: Reverses the effects, reducing rainfall in India and increasing precipitation in Southeast Asia and Australia.