Abstract
AbstractThe Quasi‐biennial Oscillation (QBO) dominates the interannual variability of the tropical stratosphere and influences other regions of the atmosphere. The high predictability of the QBO implies that its teleconnections could lead to increased skill of seasonal and decadal forecasts provided the relevant mechanisms are accurately represented in models. Here modelling and sampling uncertainties of QBO teleconnections are examined using a multi‐model ensemble of QBO‐resolving atmospheric general circulation models that have carried out a set of coordinated experiments as part of the Stratosphere‐troposphere Processes And their Role in Climate (SPARC) QBO initiative (QBOi). During Northern Hemisphere winter, the stratospheric polar vortex in most of these models strengthens when the QBO near 50 hPa is westerly and weakens when it is easterly, consistent with, but weaker than, the observed response. These weak responses are likely due to model errors, such as systematically weak QBO amplitudes near 50 hPa, affecting the teleconnection. The teleconnection to the North Atlantic Oscillation is less well captured overall, but of similar strength to the observed signal in the few models that do show it. The models do not show clear evidence of a QBO teleconnection to the Northern Hemisphere Pacific‐sector subtropical jet.
Highlights
The Quasi-Biennial Oscillation (QBO) of tropical stratospheric circulation is notable as a very long period variation that is generated by internal atmospheric processes
Since the vortex response may be associated with the occurrence of sudden stratospheric warmings (SSWs; e.g., Dunkerton et al, 1988; Andrews et al, 2019) we look for evidence for this association in the QBO initiative (QBOi) models (Section 3.3)
The strength of the Quasi-biennial Oscillation (QBO) teleconnection to the NH winter stratospheric polar vortex was shown to correlate with the amplitude of the QBO at 50 hPa, which is the altitude that shows the strongest correlation with the vortex in observations
Summary
The Quasi-Biennial Oscillation (QBO) of tropical stratospheric circulation is notable as a very long period variation that is generated by internal atmospheric processes. The oscillation is quasi-regular (periods have been observed to range between ∼20 and 36 months) and models usually can produce skilful forecasts for lead times of 3 years or more (Scaife et al, 2014b). The QBO dominates the interannual variability of the lower tropical stratosphere and influences other regions of the atmosphere. Due to the high predictability of the QBO itself, this influence may provide a source of additional seasonal and decadal predictability in those regions (Boer and Hamilton, 2008; Marshall and Scaife, 2009; Scaife et al, 2014a; Marshall et al, 2017; Garfinkel et al, 2018; O’Reilly et al, 2019; Nardi et al, 2020).
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