Sensitivity of QBO teleconnection to model circulation biases

• Published in: Scientific Reports
• Main Authors: Karpechko, A., Tyrrell, N., Rast, S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2021
• Subjects: Arctic; North Atlantic; North Atlantic oscillation
• Online Access: http://hdl.handle.net/21.11116/0000-0008-34F4-A; http://hdl.handle.net/21.11116/0000-000C-D543-8

The Quasi-biennial oscillation (QBO) in the equatorial stratospheric winds is known to modulate the extratropical atmospheric circulation so that an easterly QBO phase is associated with a weaker Arctic stratospheric vortex and a negative North Atlantic Oscillation in winter. The link can potentially be used to improve seasonal forecasts and is usually captured by climate models but with a smaller magnitude than that in observations. Here, the sensitivity of the QBO teleconnection to biases in model circulation is explored in an atmosphere-only model ECHAM6 with an internally generated QBO, by contrasting simulations by an original, biased model, and a model version in which biases are artificially reduced. We find that the strength of the winter mean Arctic stratospheric vortex response is better reproduced by the bias-corrected model. On the other hand, the response is delayed by 1 month and there is no improvement in the tropospheric response. Stronger response of the polar vortex in the bias-corrected model is likely associated with larger magnitude of QBO winds and better-represented stratospheric mean climate and planetary wave fluxes, but the exact mechanism remains unclear. The results of this study have implications for seasonal forecast model development. © 2021 Royal Meteorological Society.