Extreme weather in the Southern Hemisphere in early 2022: from Rossby waves to planetary-scale conditions

In early 2022, several extreme weather events occurred in the Southern Hemisphere. Devastating floods killed more than 500 people in South Africa (11-12 April) and about 26 people in eastern Australia (24-28 February and 25-31 March), while an unprecedented heatwave broke temperature records in Antarctica (16-22 March). This study presents a multiscale perspective of the atmospheric processes associated with these extreme events from synoptic to planetary scales. Equatorward Rossby wave breaking facilitated the transport of moist air from tropical oceans to the subtropical regions affected by the extreme precipitation events, while poleward Rossby wave breaking forced an intrusion of warm and moist extratropical air masses into the Antarctic Peninsula. Southern hemispheric extratropical wave activity demonstrated relatively normal conditions during February and March, while wave energy reached extremely large values for wave number 5 during April. From a planetary-scale perspective, we investigate how tropical variability, including the El-Nino Southern Oscillation (ENSO; in a La Nina phase) and the Madden-Julian Oscillation (MJO), modulates large-scale atmospheric circulation patterns, extratropical wave activity, and Rossby wave breaking. Overall, this study clarifies the role of regional and remote atmospheric processes in the recent weather extremes in the Southern Hemisphere.