The context of the 2018-2020 ‘protracted’ El Niño episode: Australian drought, terrestrial, marine, and ecophysiological impacts.

A ‘protracted’ El Niño episode occurred from March-April 2018 until April-May 2020. It was manifest by the interlinked Indo-Pacific influences of two components of El Niño phases. Positive Indian Ocean Dipoles (IODs) in 2018 and 2019, suppressed the formation of northwest cloud bands and southern Australia rainfall, and a persistent teleconnection, with enhanced convection generated by positive Niño 4 region sea surface temperature (SST) anomalies and strong subsidence over eastern Australia, exacerbated this Australian drought. As with ‘classical’ El Niño Southern Oscillation (ENSO) events, which usually last 12-18 months, ‘protracted’ ENSO episodes, which last for more than 2 years, show a similar pattern of impacts on society and the environment across the Indo-Pacific domain, and often extend globally. The second half of this study puts the impact of the 2018-2020 ‘protracted’ El Niño episode on both the Australian terrestrial agricultural and marine ecophysiological environments in a broader context. These impacts are often not only modulated by the direct effects of ENSO events and episodes, but by interrelated local to region ocean-atmosphere interactions and synoptic weather patterns. Even though the indices of ‘protracted’ ENSO episodes are often weaker in magnitude than those of major ‘classical’ ENSO events, it is the longer duration of the former which poses its own set of problems. Thus, there is an urgent need to investigate the potential to forecast ‘protracted’ ENSO episodes, particularly when the mid-2020 to current 2022 period has been experiencing a major ‘protracted’ La Niña episode with near-global impacts.