Indian Ocean influences on Australian climate

Sea surface temperatures

Indian Ocean sea surface temperatures impact rainfall and temperature patterns over Australia. Warmer than average sea surface temperatures can provide more moisture for frontal systems and lows crossing Australia.

Indian Ocean Dipole

Sustained changes in the difference between sea surface temperatures of the tropical western and eastern Indian Ocean are known as the Indian Ocean Dipole or IOD. The IOD is one of the key drivers of Australia's climate and can have a significant impact on agriculture. This is because events generally coincide with the winter crop growing season. The IOD has three phases: neutral, positive and negative. Events usually start around May or June, peak between August and October and then rapidly decay when the monsoon arrives in the southern hemisphere around the end of spring.


Neutral IOD phase

Water from the Pacific flows between the islands of Indonesia, keeping seas to Australia's northwest warm. Air rises above this area and falls over the western half of the Indian Ocean basin, blowing westerly winds along the equator.

Temperatures are close to normal across the tropical Indian Ocean, and hence the neutral IOD results in little change to Australia's climate.

Map diagram of Neutral IOD

Positive IOD phase

Westerly winds weaken along the equator allowing warm water to shift towards Africa. Changes in the winds also allow cool water to rise up from the deep ocean in the east. This sets up a temperature difference across the tropical Indian Ocean with cooler than normal water in the east and warmer than normal water in the west.

Generally this means there is less moisture than normal in the atmosphere to the northwest of Australia. This changes the path of weather systems coming from Australia's west, often resulting in less rainfall and higher than normal temperatures over parts of Australia during winter and spring.

Map diagram of Positive IOD

Negative IOD phase

Westerly winds intensify along the equator, allowing warmer waters to concentrate near Australia. This sets up a temperature difference across the tropical Indian Ocean, with warmer than normal water in the east and cooler than normal water in the west.

A negative IOD typically results in above-average winter–spring rainfall over parts of southern Australia as the warmer waters off northwest Australia provide more available moisture to weather systems crossing the country.

Map diagram of Negative IOD


Indian Ocean Dipole years

  1. 1960
  2. 1961
  3. 1963
  4. 1964
  5. 1972
  6. 1974
  7. 1981
  8. 1982
  9. 1983
  10. 1989
  11. 1992
  12. 1994
  13. 1996
  14. 1997
  15. 1998
  16. 2006
  17. 2010
  18. 2012
Since 1960, when reliable records of the IOD began, to 2013 there have been 9 negative IOD and 9 positive IOD events.


  1. 1960
  2. 1961
  3. 1963
  4. 1964
  5. 1972
  6. 1974
  7. 1981
  8. 1982
  9. 1983
  10. 1989
  11. 1992
  12. 1994
  13. 1996
  14. 1997
  15. 1998
  16. 2006
  17. 2010
  18. 2012
Since 1960, when reliable records of the IOD began, to 2013 there have been 9 negative IOD and 9 positive IOD events.

When the Indian and Pacific oceans work together

The El Niño–Southern Oscillation (ENSO) is the major climate driver in the Pacific Ocean and can have a strong impact on Australia's climate. El Niño years are typically warmer and drier over eastern Australia and La Niña years tend to be cooler and wetter over much of the country.

When El Niño coincides with a positive IOD, the two phenomena can reinforce their dry impacts. Likewise, when La Niña coincides with a negative IOD, the chance of above-average winter–spring rainfall typically increases.

Negative IOD years

  1. 1960
  2. 1964
  3. 1974
  4. 1981
  5. 1989
  6. 1992
  7. 1996
  8. 1998
  9. 2010

Positive IOD years

  1. 1961
  2. 1963
  3. 1972
  4. 1982
  5. 1983
  6. 1994
  7. 1997
  8. 2006
  9. 2012
Indian Ocean Dipole (IOD) years highlighting La Niña and El Niño status.