Stratosphere–Troposphere Exchange and Its Relation to Potential Vorticity Streamers and Cutoffs near the Extratropical Tropopause
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Bibliographic record
Abstract
Abstract Two distinct dynamical processes near the dynamical tropopause (2-PVU surface) and their relation are discussed in this study: stratosphere–troposphere exchange (STE) and the formation of distinct potential vorticity (PV) structures in the form of stratospheric and tropospheric streamers and cutoffs on isentropic surfaces. Two previously compiled climatologies based upon the 15-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-15) dataset (from 1979 to 1993) are used to establish and quantify the link between STE and these PV structures. An event-based analysis reveals a strong relation between the two processes. For instance, on isentropes below 320 K, 30%–50% of the stratospheric streamers are associated with downward STE. In the reverse perspective, between 60% and 80% of all STE events between 290 and 350 K are found in the vicinity of at least one PV structure. On different isentropes, the averaged downward (STT) and upward (TST) mass fluxes associated with PV structures are quantified. As a novel quantity, the activity of a particular PV structure is measured as the STT/TST flux per unit length of its boundary on the considered isentropic level. The STT activity for stratospheric streamers and the TST activity of tropospheric streamers reach similar values of 3 × 109 kg km−1 h−1. Thereby, the flux is not uniformly distributed along a streamer’s boundary. STT (TST) is found preferentially on the upstream (downstream) side of stratospheric streamers, and vice versa for tropospheric streamers. This asymmetry is lost for cutoffs, for which an essentially uniform distribution results along the boundaries. Finally, the link between STE and PV structures shows considerable geographical variability. Particularly striking is the fact that nearly all deep STT events (reaching levels below 700 hPa) over central Europe and the North American west coast are associated with a stratospheric streamer.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 it