December 4, 2025
Key points
- El Niño–Southern Oscillation (ENSO) is the foremost climatic phenomenon impacting eastern Australia in terms of intensity and spatial coverage.
- ENSO impacts large-scale atmospheric circulation to Australia directly via changes in sea level pressure related to the Southern Oscillation and indirectly through changes in Indian Ocean sea surface temperatures and associated wave trains to the Australian extra-tropics.
- Local processes driven by the surrounding sea surface temperatures and winds crucially alter evaporation, humidity and moisture advection inland, modulating rainfall patterns during ENSO events.
- The ENSO–Australian rainfall relationship is asymmetric and stronger for La Niña. This relationship varies over multidecadal cycles, peaking during the Interdecadal Pacific Oscillation negative phase.
- The influence of ENSO on Australian rainfall usually intensifies during multi-year events and is often modulated by other climate variability such as Indian Ocean Dipole, Southern Annular Mode and Madden–Julian Oscillation.
