El Niño-Southern Oscillation (ENSO) is a climate pattern that occurs in the Pacific Ocean and is one of the most important climate driver for a large portion of Australia, impacting both northern and southern regions.

During a period of El Niño, equatorial trade winds weaken and warm surface water shifts to the eastern Pacific Ocean allowing cool water to upwell in the western Pacific Ocean, which can lead to reduced rainfall and drought conditions across northern areas and eastern Australia. In contrast, during a period of La Niña, the trade winds are stronger than average, moving warm surface waters to the western Pacific Ocean while cool water upwell in the eastern Pacific Ocean, which can lead to increased rainfall and flooding across impacted regions of Australia.

An active phase of the ENSO usually occurs every 3-5 years, but can happen more frequently.

The following videos explain the impact of ENSO and how it behaves. 

Key points