Quasi-biennial oscillation disrupted by abnormal Southern Hemisphere stratosphere
Bibliographic record
Abstract
The quasi-biennial oscillation (QBO) is a repeating cycle of tropical stratosphere winds reversing direction from eastward to westward roughly every 14 months. Discovered independently by British and American scientists the QBO continued uninterrupted for 27 cycles from 1953 until February 2016 when a westward jet unexpectedly formed in the lower stratosphere during the eastward phase. This disruption is attributed to unusually high wave-momentum fluxes from the Northern Hemisphere. A second, similar, QBO disruption occurred during the 2019/2020 northern winter though wave fluxes from the Northern Hemisphere were weak. Here we show that this latest disruption to the regular QBO cycling was stronger than that seen in 2016 and resulted from horizontal momentum transport from the Southern Hemisphere during abnormal winter conditions. In both disruptions the normal downward progression of the QBO halts and the eastward shear zone above the disruption moves upward assisted by stronger tropical upwelling during the boreal winter. The predictable signal associated with the QBO’s quasi-regular phase progression is permanently lost during disruptions and the oscillation reemerges after a few months significantly shifted in phase from what would be expected if the phase had progressed uninterrupted. We infer from an increased wave-momentum flux into equatorial latitudes seen in model climate projections supporting the latest Intergovernmental Panel on Climate Change (IPCC) assessment that disruptions to the QBO are likely to be more common in future. Consequently, we anticipate that in future the QBO will be a less reliable source of predictability on lead times extending out to several years than it currently is.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".