The Small-Amplitude Dynamics of Spontaneous Tropical Cyclogenesis. Part II: Linear Stability Analysis
Bibliographic record
Abstract
Abstract This two-paper series studies the tropical cyclone (TC) precursor vortices spontaneously generated in an idealized setup with uniform sea surface temperature and no background wind. We focus on the small-amplitude stage, where vortices appear in an orderly pattern, and what controls the vortex size remains unclear. In Part I, Fourier analysis shows that the vortex size is constrained by a short-wavelength cutoff and a long-wavelength cutoff. The short-wavelength cutoff is explained as a convective spreading length due to cold pools and anvil clouds. In Part II, we study the long-wavelength cutoff. Diagnostic analysis shows that a TC precursor vortex has a shallow overturning cell in the lower troposphere and a deep overturning cell in the upper troposphere, driven by different convective types. A four-layer quasigeostrophic system is established to understand how the shallow and deep cells couple. Their dynamic coupling via midlevel buoyancy is negligible due to a midlevel high-speed waveguide that maintains a weak horizontal buoyancy gradient. Their thermodynamic coupling via the cooperative moistening of the air column is dominant. Linear stability analysis shows that the long-wavelength cutoff is controlled by an effective Rossby deformation radius Le, which is a mixture of the local Rossby deformation radii of the shallow and deep cells. The most unstable wavelength corresponds to the TC precursor vortex size, which is proportional to the geometric average of Le and the convective spreading length. The theoretical predictions generally agree with cloud-permitting simulations using varying Coriolis parameters and longwave radiative feedback strengths.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".