ITCZ Breakdown and Its Upscale Impact on the Planetary-Scale Circulation over the Eastern Pacific
Bibliographic record
Abstract
Abstract The eastern Pacific (EP) intertropical convergence zone (ITCZ) is sometimes observed to break down into several vortices on the synoptic time scale. It is still a challenge for present-day numerical models to simulate the ITCZ breakdown in the baroclinic modes. Also, the upscale impact of the associated mesoscale fluctuations on the planetary-scale circulation is not well understood. Here, a simplified multiscale model for the modulation of the ITCZ is used to study these issues. A prescribed two-scale heating drives the planetary-scale circulation through both planetary-scale mean heating and eddy flux divergence of zonal momentum, where the latter represents the upscale impact of mesoscale disturbances. In an idealized scenario where the heating only varies on the mesoscale, key features of the ITCZ breakdown in the baroclinic modes are captured. The eddy flux divergence of zonal momentum is characterized by midlevel (low level) eastward (westward) momentum forcing at subtropical latitudes of the Northern Hemisphere and opposite-signed midlevel momentum forcing at low latitudes. Such upscale impact of mesoscale fluctuations tends to accelerate (decelerate) planetary-scale zonal jets in the middle (lower) troposphere. Compared with deep heating, shallow heating induces stronger vorticity anomalies on the mesoscale and more significant eddy flux divergence of zonal momentum and acceleration–deceleration effects on the planetary-scale mean flow. In a more realistic scenario where the heating also varies on the planetary scale, the most significant zonal velocity anomalies are confined in the diabatic heating region.
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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 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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".