Context: Two Australian weather agencies recently forecasted the potential re-emergence of the Positive Indian Ocean Dipole (IOD), or Indian Nino, for the second consecutive year in the latter half of 2024.

Indian Ocean Dipole

• About: It sometimes dubbed as the "Indian Nino," occurs in the Indian Ocean between the Indonesian and Malaysian coastline in the east and the African coastline near Somalia in the west.
• Discovery and Recognition: The Indian Ocean Dipole was independently identified as a distinct climatic phenomenon in 1999.
• Positive Indian Ocean Dipole (IOD): It is characterized by cooler than normal sea-surface temperatures (SST) in the eastern equatorial Indian Ocean and warmer than normal SSTs in the western tropical Indian Ocean.
• Negative Indian Ocean Dipole (IOD): It displays warmer than normal SSTs in the eastern equatorial Indian Ocean and cooler than normal SSTs in the western tropical Indian Ocean.
• Relationship with El Nino and La Nina: A positive IOD often coincides with El Nino, while a negative IOD is sometimes associated with La Nina.
• Impact: Positive IOD events enhance rainfall along the African coastline and the Indian sub-continent but suppress rainfall over Indonesia, southeast Asia, and Australia. Conversely, the impacts reverse during negative IOD events.