Indian Ocean Dipole (IOD)
Meat & Livestock Australia October 20, 2023
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.
During a positive IOD phase the tropical west Indian Ocean sea surface temperatures (SSTs) are warmer than usual, which can lead to reduced rainfall across central and 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 across central and southern Australia.
The following videos explain the impact of IOD and how it behaves.
Key points
- There are 3 phases for the IOD: IOD positive (typically dry), neutral (not active), IOD negative (typically wet).
- IOD events start in winter, peak over spring, and then rapidly decay at the end of spring/beginning of summer.
- IOD can impact springtime temperatures, making them unusually warm or cool.
- It would be very unusual for an IOD event to last into January, but it can happen.
- A very strong IOD event can hasten or delay the start of the northern wet season.
- IOD interacts with ENSO, such that positive IOD often occurs with El Niño, and negative IOD often occurs with La Niña. The co-occurrence of these two drivers can strengthen the impacts.