Preprints
https://doi.org/10.5194/wcd-2020-56
https://doi.org/10.5194/wcd-2020-56

  10 Nov 2020

10 Nov 2020

Review status: a revised version of this preprint was accepted for the journal WCD and is expected to appear here in due course.

Origins of Multi-decadal Variability in Sudden Stratospheric Warmings

Oscar Dimdore-Miles1, Lesley Gray1,2, and Scott Osprey1,2 Oscar Dimdore-Miles et al.
  • 1Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, OX1 3PU, UK
  • 2National Centre for Atmospheric Science, Oxford, OX1 3PU

Abstract. Sudden Stratospheric Warmings (SSWs) are major disruptions of the Northern Hemisphere (NH) stratospheric polar vortex and occur on average approximately 6 times per decade in observation based records. However, within these records, intervals of significantly higher and lower SSW rates are observed suggesting the possibility of low frequency variations in event occurrence. A better understanding of factors that influence this decadal variability may help to improve predictability of NH mid-latitude surface climate, through stratosphere-troposphere coupling. In this work, multi-decadal variability of SSW events is examined in a 1000-yr pre-industrial simulation of a coupled Atmosphere-Ocean-Land-Sea ice model. Using a wavelet spectral decomposition method, we show that hiatus events (intervals of a decade or more with no SSWs) and consecutive SSW events (extended intervals with at least one SSW in each year) vary on multi-decadal timescales of period between 60 and 90 years. Signals on these timescales are present for approximately 450 years of the simulation. We investigate the possible source of these long-term signals and find that the direct impact of variability in tropical sea surface temperatures, as well as the associated Aleutian Low, can account for only a small portion of the SSW variability. Instead, the major influence on long-term SSW variability is associated with long-term variability in amplitude of the stratospheric quasi biennial oscillation (QBO). The QBO influence is consistent with the well known Holton-Tan relationship, with SSW hiatus intervals associated with extended periods of particularly strong, deep QBO westerly phases. The results support recent studies that have highlighted the role of vertical coherence in the QBO when considering coupling between the QBO, the polar vortex and tropospheric circulation.

Oscar Dimdore-Miles et al.

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Oscar Dimdore-Miles et al.

Oscar Dimdore-Miles et al.

Viewed

Total article views: 469 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
336 128 5 469 7 3
  • HTML: 336
  • PDF: 128
  • XML: 5
  • Total: 469
  • BibTeX: 7
  • EndNote: 3
Views and downloads (calculated since 10 Nov 2020)
Cumulative views and downloads (calculated since 10 Nov 2020)

Viewed (geographical distribution)

Total article views: 413 (including HTML, PDF, and XML) Thereof 410 with geography defined and 3 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 26 Feb 2021
Download
Short summary
Observations of the stratosphere span roughly half a century preventing analysis of multi-decadal variability in circulation using these data. Instead, we rely on long simulations of climate models. Here, we use a model to examine variations in northern polar stratospheric winds and find they vary with a period of around 90 years. We show that this is possibly due to variations in the size of winds over the equator. This result may improve understanding of equator-polar stratospheric coupling.