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Sensitivity of QBO teleconnection to model circulation biases
Quarterly Journal of the Royal Meteorological Society ( IF 3.0 ) Pub Date : 2021-03-04 , DOI: 10.1002/qj.4014
Alexey Yu Karpechko 1 , Nicholas L. Tyrrell 1 , Sebastian Rast 2
Affiliation  

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.

中文翻译:

QBO遥相关对模拟环流偏差的敏感性

众所周知,赤道平流层风中的准双年振荡 (QBO) 会调节温带大气环流,因此东风 QBO 阶段与较弱的北极平流层涡旋和冬季的负北大西洋涛动有关。该链接可用于改进季节性预测,通常由气候模型捕获,但幅度小于观测值。在这里,QBO 遥相关对模型环流偏差的敏感性在带有内部生成的 QBO 的仅大气模型 ECHAM6 中进行了探索,通过对比原始、有偏差的模型和人为减少偏差的模型版本的模拟。我们发现冬季平均北极平流层涡旋响应的强度可以通过偏差校正模型更好地再现。另一方面,响应延迟1个月,对流层响应没有改善。偏差校正模型中极地涡旋的更强响应可能与更大规模的 QBO 风和更好地代表平流层平均气候和行星波通量有关,但确切机制仍不清楚。这项研究的结果对季节性预测模型的开发具有影响。
更新日期:2021-03-04
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