Optimizing the definition of a sudden stratospheric warming

Amy H. Butler, Edwin P. Gerber

Research output: Contribution to journalArticlepeer-review


Various criteria exist for determining the occurrence of a major sudden stratospheric warming (SSW), but the most common is based on the reversal of the climatological westerly zonal-mean zonal winds at 60° latitude and 10 hPa in the winter stratosphere. This definition was established at a time when observations of the stratosphere were sparse. Given greater access to data in the satellite era, a systematic analysis of the optimal parameters of latitude, altitude, and threshold for the wind reversal is now possible. Here, the frequency of SSWs, the strength of the wave forcing associated with the events, changes in stratospheric temperature and zonal winds, and surface impacts are examined as a function of the stratospheric wind reversal parameters. The results provide a methodical assessment of how to best define a standard metric for major SSWs. While the continuum nature of stratospheric variability makes it difficult to identify a decisively optimal threshold, there is a relatively narrow envelope of thresholds that work well-and the original focus at 60° latitude and 10 hPa lies within this window.

Original languageEnglish (US)
Pages (from-to)2337-2344
Number of pages8
JournalJournal of Climate
Issue number6
StatePublished - Mar 1 2018


  • Classification
  • Stratosphere
  • Stratosphere-troposphere coupling
  • Stratospheric circulation

ASJC Scopus subject areas

  • Atmospheric Science


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