Structure and dynamics of an Alpine potential‐vorticity banner
Notice bibliographique
Résumé
Abstract A detailed analysis is undertaken of the primary Alpine shear zone that occurred on 1 October 1999 during the Mesoscale Alpine Programme. This shear zone emanates from the south‐western Alpine tip in north‐westerly flow conditions, develops in response to the Alpine‐scale flow splitting, and separates the northerly mistral wind to the south‐west of the Alps from the quasi‐stagnant air within the Alpine wake. The study is based on in situ flight‐level and dropsonde data from two research aircraft. The data are used for the construction of an objective analysis in a cross‐section perpendicular to the shear zone, and for diagnostic computations of the potential‐vorticity (PV) flux between vertically stacked flight legs. The observed flow structure is compared with simulation results of the Swiss Model and the non‐hydrostatic Canadian Mesoscale Compressible Community Model (MC2), operating at horizontal resolutions of 14 and 3 km, respectively. Immediately downstream of the topography, the observed shear zone has a surprisingly quasi‐steady structure that becomes evident provided a slow westward migration is accounted for. Further downstream, the shear zone shows increased signs of transience. Near the surface, it has an overall width of ∼150 km, but narrows to about 25 km near the top of the mistral inversion at a height of ∼2 km. Detailed analysis shows that the shear zone has a complex substructure consisting of at least three positive and three negative PV filaments. These shear lines are characterized by a pronounced vertical coherence in the mixed layer and throughout most of the inversion layer. One of the banners is also evident in low‐level tracer constituents. Diagnostic computations of the PV flux along the banners using the generalized Bernoulli theorem reveal that most of the associated PV flux is due to vertically oriented vorticity within the inversion layer. Within the shear zone, there is a spanwise circulation of appreciable strength. It consists of a deformation flow with the axes of deformation oriented perpendicular to the shear zone. This deformation flow in effect squeezes the PV banners and thereby makes them resilient with respect to dissipation and barotropic instabilities. Detailed intercomparison with numerical model results shows that models with a grid spacing below ∼15 km are able to capture the overall structure of the shear zone. The MC2 model in addition credibly replicates some of the finer‐scale sub‐structure of the shear zone, in particular at low levels. The high predictability and steadiness of the PV banners supports the idea that individual banners are generated by flow‐separation and/or gravity‐wave breaking events upstream. It is argued that the overall width of the shear zone is thus in effect determined by the geometry of the upstream topography and the dynamical processes that govern the downstream advection of the PV banners. Copyright © 2003 Royal Meteorological Society.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».