Australian rainfall and dipole-like sea surface temperature patterns in the Indian Ocean

Pete Lamb had an intense and long-standing interest in the Indian Ocean and the rainfall variations of countries bordering this ocean. His initiatives helped us understand much more about rainfall variations and change, and of the climate of the Indian Ocean, and he helped climate scientists from many countries bordering the Ocean to start their careers in climate research, especially through the extended (six-week) Regional Climate Prediction and Applications Workshops he organised and led at the University of Oklahoma. I was privileged to help Pete by lecturing at two of these training workshops. I am also indebted to him because he convinced me to be an editor of the Journal of Climate (1997-2003). He was especially proud, I think, that he had managed to convince, for the first time, a scientist resident outside North America to be an editor of the journal (of which, of course, Pete was the founding Chief Editor). He also introduced me to the fascinating worlds of professional baseball and college football.

In the first year of Pete's Chief Editorship I published, in the Journal of Climate, a paper describing the relationship between interannual Australian rainfall variability and a dipole-like pattern of sea surface temperature variations in the Indian Ocean (Nicholls, 1989). Previous work over many decades had documented the influence of the El Niño – Southern Oscillation on Australian rainfall variability, including the spatial pattern of the influence of ENSO. One intriguing aspect of the ENSO-rainfall relationship was that the phenomenon was less influential along the southern edge of the Australian continent, compared to its impact in inland eastern Australia (eg., McBride and Nicholls, 1983). Variations in the dipole-like SST pattern in the Indian Ocean, as the 1989 paper demonstrated, were closely linked to rainfall variations along the southern part of the continent, as well as through the centre and northwest. Patterns of sea surface temperature variability subsequently joined patterns related to the ENSO as predictors in the Bureau of Meteorology's operational seasonal rainfall forecast system (Drosdowsky and Chambers, 2001). Further work by many scientists has documented more clearly the presence of Indian Ocean dipole-like patterns, proposed mechanisms for their development, and related variations in these patterns to changes and variations in rainfall in various parts of the world, including Australia. I will review the research of the past 25 years regarding relationships between Indian Ocean sea surface temperature “dipoles” and Australian rainfall.

Drosdowsky, W and Chambers, LE, 2001. Near-global sea surface temperature anomalies as predictors of Australian seasonal rainfall. J. Climate, 14, 1677-1687.

McBride, JL and Nicholls, N. 1983. Seasonal relationships between Australian rainfall and the Southern Oscillation. Mon. Weath. Rev., 111, 1998-2004.

Nicholls, N. 1989. Sea surface temperature and Australian winter rainfall. J. Climate, 2, 965-973.