Preprints
https://doi.org/10.5194/wcd-2022-42
https://doi.org/10.5194/wcd-2022-42
 
26 Jul 2022
26 Jul 2022
Status: this preprint was under review for the journal WCD. A revision for further review has not been submitted.

Revisiting the wintertime emergent constraint of the Southern Hemispheric midlatitude jet response to global warming

Philipp Breul1, Paulo Ceppi1,2, and Theodore Gordon Shepherd3 Philipp Breul et al.
  • 1Department of Physics, Imperial College London, London, United Kingdom
  • 2Grantham Institute, Imperial College London, London, United Kingdom
  • 3Department of Meteorology, University of Reading, Reading, United Kingdom

Abstract. Most climate models show a poleward shift of the southern hemispheric jet in response to climate change, but the inter-model spread is large. In an attempt to constrain future jet responses, past studies have identified an emergent constraint between the climatological jet latitude and the future jet shift in austral winter. However, we show that the emergent constraint only arises in the zonal mean, and not in separate halves of the hemisphere. This can be explained by the presence of a double jet structure in the Pacific region, making the zonal mean jet latitude a poorly defined quantity that does not represent the latitude of a zonally coherent structure during this season. The usefulness of the emergent constraint is therefore questionable. This finding can further explain the prior finding among CMIP5 and CMIP6 ensembles that the meridional structure of the zonal-mean zonal wind response does not change with climatological jet latitude but stays fixed.

Philipp Breul et al.

Status: closed (peer review stopped)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2022-42', Anonymous Referee #1, 21 Aug 2022
  • RC2: 'Comment on wcd-2022-42', Anonymous Referee #2, 18 Sep 2022
  • AC1: 'Comment on wcd-2022-42', Philipp Breul, 14 Oct 2022

Status: closed (peer review stopped)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2022-42', Anonymous Referee #1, 21 Aug 2022
  • RC2: 'Comment on wcd-2022-42', Anonymous Referee #2, 18 Sep 2022
  • AC1: 'Comment on wcd-2022-42', Philipp Breul, 14 Oct 2022

Philipp Breul et al.

Philipp Breul et al.

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Short summary
Accurately predicting the response of the mid-latitude jet stream to climate change is very important, but climate models show a variety of possible scenarios. Previous work has identified a relationship between climatological jet latitude and future jet shift in the southern hemispheric winter. However, we show that the jet latitude is not a well-defined metric in in austral winter, due to zonal asymmetries in the mid-latitude jet. The usefulness of the relationship is therefore questionable.