07 Mar 2022
07 Mar 2022
Status: this preprint is currently under review for the journal WCD.

The tropical route of QBO teleconnections in a climate model

Jorge L. García-Franco1, Lesley J. Gray1,2, Scott Osprey1,2, Robin Chadwick3,4, and Zane Martin5 Jorge L. García-Franco et al.
  • 1Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK
  • 2National Centre for Atmospheric Science, UK
  • 3Met Office Hadley Centre, Exeter, UK
  • 4Global Systems Institute, Department of Mathematics, University of Exeter, Exeter, UK
  • 5Department of Atmospheric Science, Colorado State University, Fort Collins, CO

Abstract. The influence of the quasi-biennial oscillation (QBO) on tropical climate is demonstrated using a 500-yr pre-industrial control simulation of the Met Office Hadley Centre model. Robust precipitation responses to the phase of the QBO are diagnosed in the model which show zonally asymmetric features, consistent with observational studies. The response in precipitation resembles the El Niño-Southern Oscillation (ENSO) impacts, however, regression analysis shows that there is a QBO signal in precipitation that is independent from ENSO. Moreover, the observed uneven frequency of ENSO events for each QBO phase is also found in these simulations, with more El Niño events found under the westerly phase of the QBO (QBOW) and more La Niña events for the easterly phase (QBOE). No evidence is found to suggest that these QBO-ENSO relationships are caused by ENSO modulating the QBO in the simulations. A previously unknown relationship between the QBO and a dipole of precipitation in the Indian Ocean is found in models and observations in boreal fall, characterized by a wetter western Indian Ocean and drier conditions in the eastern part for QBOW and the opposite under QBOE conditions. QBO W-E differences show a stronger East Pacific Inter-tropical Convergence Zone (ITCZ) in boreal winter and a northward shift of the Atlantic ITCZ in boreal spring and summer. The Walker circulation is found to be significantly weaker during QBOW compared to QBOE, explaining the observed and simulated zonally asymmetric responses at equatorial latitudes. Further work, including targeted model experiments, is required to betters understand the mechanisms causing these relationships between the QBO and tropical convection.

Jorge L. García-Franco et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2022-14', Anonymous Referee #1, 28 Mar 2022
  • RC2: 'Comment on wcd-2022-14', Anonymous Referee #2, 28 Mar 2022
  • RC3: 'Comment on wcd-2022-14', Anonymous Referee #3, 13 Apr 2022
  • AC1: 'Comment on wcd-2022-14', Jorge Luis Garcia-Franco, 13 May 2022

Jorge L. García-Franco et al.

Jorge L. García-Franco et al.


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Short summary
This paper establishes robust links between the stratosphere, via a semi-periodical oscillation and tropical surface climate. Surface responses as well as several features of the tropical circulation are found to be robustly linked to the variability in the tropical stratosphere in a long simulation of a state-of-the-art climate model which suggests that processes exist that couple the two bottom layers of the atmosphere and that can affect the tropical surface.