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Lifecycle of Major Sudden Stratospheric Warmings in the Southern Hemisphere from a Multi-Millennial GCM Simulation
  • Martin Jucker,
  • Thomas Reichler
Martin Jucker
University of New South Wales

Corresponding Author:martin.jucker@unsw.edu.au

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Thomas Reichler
University of Utah
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Sudden Stratospheric Warmings (SSWs) are rare in the Southern Hemisphere (SH), making it difficult to study possible precursors or subsequent impacts. Using a multi-millennial coupled climate model simulation producing 161 SSWs in the SH, we present a detailed study of their lifecycle. We show that SH SSWs are predominantly displacement events forced by wave-1 planetary waves, and that the surface signature similar to the negative phase of the Southern Annular Mode (SAM) is detectable up to two months before the onset date, but there is a tendency for a transition from wave-1 before to zonally symmetric anomalies after onset. We identify a strong weakening of the Amundsen Sea Low as one of the most prominent precursors, which weakens the climatological wave-2 and wave-3 stationary waves and strengthens wave-1 forcing. Compared to their northern counterparts, SH SSWs generally have a longer timescale, and while there is evidence of pre-onset forcing related to tropical sea surface temperatures, the Indian Ocean Dipole is more important than the El Niño Southern Oscillation.