Extreme weather in the Southern Hemisphere in early 2022

Abstract In early 2022, several exceptionally extreme weather events struck the Southern Hemisphere. Deadly floods affected eastern Australia and South Africa, and an unprecedented heatwave in East Antarctica broke global temperature anomaly records. This study presents a multi-scale analysis of the atmospheric processes leading to these extreme events ranging from local to planetary scales. While the subtropical flood events were associated with slow-moving circulation patterns with moderate departures from climatology, the Antarctic heatwave was unprecedented with surface temperatures and atmospheric moisture content breaking records in observation-based data since 1979. Despite the variety in weather type and region, all three extreme events share the commonality that they result from extratropical Rossby wave breaking modulated by tropical variability on intraseasonal to interannual timescales. Equatorward wave breaking steered moisture transport from nearby oceans towards the subtropical flood regions favored by anticyclonic circulation anomalies in the midlatitudes and a poleward displaced midlatitude jet. Enhanced tropical convection over the Indian Ocean promoted poleward-eastward Rossby wave propagation eventuating in poleward wave breaking that forced an intrusion of exceptionally warm and moist air masses into the Antarctic continent. At seasonal timescales, large parts of the study regions experienced record-breaking surface weather associated with the influence of La Nina setting up favorable circulation patterns for heavy precipitation over the eastern Australian and South African coasts and heatwave occurrence over East Antarctica’s interior. This study contributes to an improved process-understanding of extreme weather events in the Southern Hemisphere with implications for weather and climate prediction of such events.