QBOi – Towards Improving the Quasi-Biennial Oscillation in Global Climate Models

workshop on the QBO, including its teleconnections and couplings to atmospheric composition, and general developments in wave-mean-flow processes in the atmosphere

27 – 31 March 2023,

Oxford, UK

Activity Leaders

Scott Osprey
NCAS, University of Oxford, UK

Neal Butchart
Hadley Centre, UK

James Anstey
CCCMA, Canada

Yaga Richter

Yoshio Kawatani
Hokkaido University, Japan


  • Charles McLandress, University of Toronto, Canada
  • George Boer, CCCMA, Canada
  • Norm McFarlane, CCCMA, Canada
  • John Scinocca, CCCMA, Canada
  • Michael Sigmond, CCCMA, Canada
  • Bo Christiansen, DMI, Denmark
  • Shuting Yang, DMI, Denmark
  • Albert Hertzog, LMD, France
  • Francois Lott, LMD, France
  • Riwal Plougonven, LMD, France
  • Peter Braesicke, KIT, Germany
  • Elisa Manzini, MPI, Germany
  • Hauke Schmidt, MPI, Germany
  • Chiara Cagnazzo, CMCC, Italy
  • Shingo Watanabe, JAMSTEC, Japan
  • Shigeo Yoden, University of Kyoto, Japan
  • Hye Yeong-Chun, Yonsei University, Korea
  • Young-Ha Kim, Yonsei University, Korea
  • Tim Stockdale, ECMWF, UK
  • Mark Baldwin, University of Exeter, UK
  • Andrew Bushell, Met Office
  • Adam Scaife, Met Office Hadley Centre, UK
  • Lesley Gray, NCAS, University of Oxford, UK
  • Verena Schenzinger, University of Oxford, UK
  • Christiane Jablonowski, University of Michigan, USA
  • Alan Plumb, MIT, USA
  • Julio Bacmeister, NCAR, USA
  • Rolando Garcia, NCAR, USA
  • Hanli Liu, NCAR, USA
  • Anne Smith, NCAR, USA
  • Tim Dunkerton, NWRA, USA
  • Marv Geller, Stony Brook, USA
  • David Rind, NASA-GISS, USA
  • Kohei Yoshida, MRI, Japan
  • Federico Serva, CMCC, Italy
  • Javier Garcia-Serrano, BSC-CNS, Spain
  • Laura Holt, NWRA, USA
  • Pu Lin, Princeton, USA
  • Isla Simpson, NCAR, USA
  • Jack Chen, NCAR, USA

Activity description

Until recently, only a small number of global climate models have successfully captured realistic tropical stratosphere variability. The most conspicuous manifestation of this variability is the quasi-biennial oscillation – known to have the longest naturally occurring timescale within the climate system. This tropical phenomenon is important to the redistribution of minor trace gas species involved in ozone chemistry and teleconnections linked with high latitude weather.

Of the climate models participating in the Chemistry-Climate Model Validation Activity Phase 2, only two reported an internally generated QBO, seven chose nudging toward observations, while the remainder had no realistic QBO variability. Furthermore, in the recent WCRP Coupled Model Intercomparison Project – Phase 5 (CMIP5), only three models captured a realistic QBO. In a recent study exploring the effects of future climate change on tropical stratosphere variability, Kawatani and Hamilton (2013) reported a weakening of the QBO amplitude into the 21st Century. This result was consistent with increased tropical upwelling following a strengthening of the Brewer-Dobson circulation. However, no robust response was found for projected changes to the QBO period.

The objective of QBOi is to improve the fidelity of tropical stratosphere variability in present-day GCMs. This will be achieved by: (1) evaluating past and present-day modelled QBO variability and (2) soliciting the participation of modelling groups to design numerical experiments to explore the sensitivity dependencies of tropical stratosphere variability in current GCMs. Examples of these dependencies include details such as vertical resolution, wave parameterisations, etc. Our intention is that this will provide a ‘recipe book’ for simulating a reliable QBO, informing models contributing to future CMIP experiments and for numerical weather forecasters.

QBOi is focussed on modelling studies, but benefits from other SPARC activities, such as: Gravity Waves (for constraining parameter estimates within GCMs) and the Data Assimilation Working Group project S-RIP: SPARC Reanalysis/Analysis Intercomparison Project (providing wave climatologies). Output from QBOi will also benefit programmes such as the Working Group for Numerical Experimentation (evaluating process uncertainty), the Working Group on Seasonal to Interannual Prediction (identifying pathways for predictability), and within SPARC, CCMI (tracer transport) and DynVar (stratosphere-troposphere coupling).

During phase 1, a workshop was held to agree on a set of coordinated multi-model experiments and essential diagnostics (QBO Modelling and Reanalysis Workshop, 16-18 March 2015, Victoria, Canada). Progress was made toward agreeing a table of QBO metrics for future studies. The common set of experiments and diagnostics have subsequently been finalised and published on the QBOi project web page (see below).

Second and third workshops were held in 2016 (Oxford) and 2017 (Kyoto, joint with SATIO-TCS and FISAPS), as reported in SPARC newsletters no. 48 and 50. Publication of the core papers in a QJRMS Special Section on QBO modelling intercomparison completes QBOi phase 1.

Planning for phase 2 of QBOi began at the 2018 SPARC GA and will involve new experiments and analyses to address the key outstanding questions identified in phase 1.

Published results

Phase 1 core papers:

Anstey, J.A., Butchart, N., Hamilton, K., Osprey, S.M. (2020): The SPARC Quasi‐Biennial Oscillation initiative. Quarterly Journal Of The Royal Meteorological Society, doi: 10.1002/qj.3820

A. C. Bushell et al., 2020: Evaluation of the Quasi-Biennial Oscillation in global climate models for the SPARC QBO-initiative. Quarterly Journal Of The Royal Meteorological Society, doi:10.1002/qj.3765.

J. Richter et al. 2020: Response of the quasi-biennial oscillation to a warming climate in global climate models. Quarterly Journal Of The Royal Meteorological Society, doi:10.1002/qj.3749.

T. N. Stockdale et al., 2020: Prediction of the quasi-biennial oscillation with a multi-model ensemble of QBO -resolving models. Quarterly Journal Of The Royal Meteorological Society, doi:10.1002/qj.3919.

LA. Holt, .et al., 2020: An evaluation of tropical waves and wave forcing of the QBO in the QBOi models. Quarterly Journal Of The Royal Meteorological Society, doi:10.1002/qj.3827.

Anstey, J.A. et al., 2021: Teleconnections of the Quasi-Biennial Oscillation in a multi-model ensemble of QBO-resolving models. Quarterly Journal Of The Royal Meteorological Society, doi: 10.1002/qj.4048

AK. Smith et a., 2019: The equatorial stratospheric semiannual oscillation and time-mean winds in QBOi models. Quarterly Journal Of The Royal Meteorological Society, doi:10.1002/qj.3690

Other key publications:

Anstey, J.A., et al., 2022: Impacts, processes and projections of the quasi-biennial oscillation. Nat Rev Earth Environ, doi: 10.1038/s43017-022-00323-7

Serva, F., et al., 2022: The impact of the QBO on the region of the tropical tropopause in QBOi models: Present-day simulations. Q J R Meteorol Soc, 148( 745), 1945– 1964. doi: 10.1002/qj.4287

Anstey, J.A., et al., 2021: Prospect of increased disruption to the QBO in a changing climate. Geophysical Research Letters, 48, e2021GL093058. doi: 10.1029/2021GL093058

N. Butchart et al., 2020: QBO changes in CMIP6 climate projections. Geophysical Research Letters, doi:10.1029/2019gl086903.

J. Richter, J et al., 2020: Simpson, Isla R.; Progress in Simulating the Quasi-Biennial Oscillation in CMIP Models. Journal Of Geophysical Research: Atmospheres, 125 (8), doi:10.1029/2019jd032362.

Naoe, H. and Yoshida, K., 2019: Influence of quasi‐biennial oscillation on the boreal winter extratropical stratosphere in QBOi experiments. Quarterly Journal of the Royal Meteorological Society, 145(723), pp.2755-2771.

Butchart, N. et al., 2018. Overview of experiment design and comparison of models participating in phase 1 of the SPARC Quasi-Biennial Oscillation initiative (QBOi). Geoscientific Model Development, 11, 1009-1032, 10.5194/gmd-11-1009-2018.

Osprey, S., Geller M., and Yoden S., 2018: The stratosphere and its role in tropical teleconnections. Eos. 2018 99, 10.1029/2018EO097387.

Watanabe S., Hamilton K., Osprey S., Kawatani Y., Nishimoto N., 2018: First Successful Hindcasts of the 2016 Disruption of the Stratospheric Quasi-biennial Oscillation. Geophys. Res. Lett., 45(3), 10.1002/2017GL076406.

Schenzinger V., Osprey S., Gray L., Butchart N., 2017: Defining metrics of the Quasi-Biennial Oscillation in global climate models. Geosci Model Dev., 8 Jun 2017, 10(6):2157-68, DOI: 10.5194/gmd-10-2157-2017

Osprey, S. M., N. Butchart, J. R. Knight, A. Scaife, K. Hamilton, J. A. Anstey, V. Schenzinger, and C. Zhang, 2016: An unexpected disruption of the atmospheric quasi-biennial oscillation. Science, 08 Sep 2016, DOI: 10.1126/science.aah4156

Hamilton, K., S. Osprey, and N. Butchart, 2015: Modeling the stratosphere’s “heartbeat,” EOS, 96, doi:10.1029/2015EO032301.

SPARC activity updates:

SPARC Newsletter No. 57, 2021, p. 12: Improving the QBO in climate models, by James Anstey, Neal Butchart, Kevin Hamilton, Scott Osprey, Andrew Bushell, Laura Holt, Yaga Richter, Anne Smith and Tim Stockdale .

SPARC Newsletter No. 50, 2018, p. 19: Report on the Joint SPARC Dynamics and Observations Work- shop: SATIO-TCS, FISAPS and QBOi, Kyoto, Japan, by James Anstey, Shigeo Yoden, Marvin Geller, Scott Osprey, Kevin Hamilton, Neal Butchart

SPARC Newsletter No. 48, 2017, p. 33: Report on the SPARC QBO Workshop: The QBO and its Global Influence – Past, Present and Future, by Anstey, J., S. Osprey, N. Butchart, K. Hamilton, L. Gray and M. Baldwin

SPARC Newsletter No. 45, 2015, p. 19: Report on the 1st QBO Modelling and Reanalyses Workshop, by Anstey, J., K. Hamilton, S. Osprey, N. Butchart, and L. Gray

Website for further information