Interactions between Pacific and Indian Ocean variability and impacts on Australian rainfall
Zoe Gillett
Australia’s climate is strongly influenced by variations in sea surface temperatures (SSTs) in the tropical Pacific and Indian Oceans. The El Niño-Southern Oscillation (ENSO) modulates rainfall in eastern and northern Australia, particularly during the austral spring, while the Indian Ocean Dipole (IOD) affects the southeast and southwest in winter and spring. The Indian Ocean Basin Mode (IOBM) extends ENSO’s influence into late summer over northern Australia. These climate modes often interact, amplifying their effects across Australia. To disentangle these interactions, we conducted pacemaker-style simulations using ACCESS-CM2 to isolate the individual and combined contributions of SST variability in the tropical Indian and Pacific Oceans to Australian rainfall. We analyse changes in ENSO variability when interannual SST variability in the tropical Indian Ocean is suppressed, and similarly examine the IOD and IOBM under suppressed tropical Pacific Ocean SST variability. We also examine how these changes affect teleconnections to Australian rainfall, focusing on shifts in the mean, variability, and extremes. Finally, we link these rainfall changes to changes in the large-scale atmospheric circulation.
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