The Indian Ocean Dipole (IOD) is a climate pattern that occurs in the tropical Indian Ocean, which can also have a significant impact on rainfall patterns across Australia. The IOD is second in importance, behind ENSO, for driving Australia’s seasonal climate.

The IOD is usually finished by the start of the northern wet season, so most of the time it has little direct impact, though it has stronger impacts in other areas of Australia, like southeast Australia.

During a positive IOD phase the tropical west Indian Ocean sea surface temperatures (SSTs) are warmer than usual, which can lead to reduced rainfall and drought conditions across southern Australia. In contrast, during a negative IOD phase, the tropical east Indian Ocean SSTs are warmer than average, which can lead to increased rainfall and flooding across southern Australia.

The following videos explain the impact of IOD and how it behaves. 

Key points