Moist Teleconnection Mechanisms for the Tropical South American and Atlantic Sector*
Notice bibliographique
Résumé
Abstract Teleconnections have traditionally been studied for the case of dry dynamical response to a given diabatic heat source. Important anomalies often occur within convective zones, for instance, in the observed remote response to El Niño. The reduction of rainfall and teleconnection propagation in deep convective regions poses theoretical challenges because feedbacks involving convective heating and cloud radiative effects come into play. Land surface feedbacks, including variations of land surface temperature, and ocean surface layer temperature response must be taken into account. During El Niño, descent and negative precipitation anomalies often extend across equatorial South America and the Atlantic intertropical convergence zone. Analysis of simulated mechanisms in a case study of the 1997/98 El Niño is used to illustrate the general principals of teleconnections occurring in deep convective zones, contrasting land and ocean regions. Comparison to other simulated events shows similar behavior. Tropospheric temperature and wind anomalies are spread eastward by wave dynamics modified by interaction with the moist convection zones. The traditional picture would have gradual descent balanced by radiative damping, but this scenario misses the most important balances in the moist static energy (MSE) budget. A small “zoo” of mechanisms is active in producing strong regional descent anomalies and associated drought. Factors common to several mechanisms include the role of convective quasi equilibrium (QE) in linking low-level moisture anomalies to free tropospheric temperature anomalies in a two-way interaction referred to as QE mediation. Convective heating feedbacks change the net static stability to a gross moist stability (GMS) M. The large cloud radiative feedback terms may be manipulated to appear as a modified static stability Meff, under approximations that are quantified for the quasi-equilibrium tropical circulation model used here. The relevant measure of Meff differs between land, where surface energy flux balance applies, and short time scales over ocean. For the time scale of an onsetting El Niño, a mixed layer ocean response is similar to a fixed sea surface temperature (SST) case, with surface fluxes lost into the ocean and Meff substantially reduced over ocean-enhancing descent anomalies. Use of Meff aids analysis of terms that act as the initiators of descent anomalies. Apparently modest terms in the MSE budget can be acted on by the GMS multiplier effect, which yields substantial precipitation anomalies due to the large ratio of the moisture convergence to the MSE divergence. Advection terms enter in several mechanisms, with the leading effects here due to advection by mean winds in both MSE and momentum balances. A Kelvinoid solution is presented as a prototype for how easterly flow enhances moist wave decay mechanisms, permitting relatively small damping terms by surface drag and radiative damping to produce the substantial eastward temperature gradients seen in observations and simulations and contributing to precipitation anomalies. The leading mechanism for drought in eastern equatorial South America is the upped-ante mechanism in which QE mediation of teleconnected tropospheric temperature anomalies tends to produce moisture gradients between the convection zone, where low-level moisture increases toward QE, and the neighboring nonconvective region. Over the Atlantic ITCZ, the upped-ante mechanism is a substantial contributor, but on short time scales several mechanisms referred to jointly as troposphere/SST disequilibrium mechanisms are important. While SST is adjusting during passive SST (coupled ocean mixed layer) experiments, or for fixed SST, heat flux to the ocean is lost to the atmosphere, and these mechanisms can induce descent and precipitation anomalies, although they disappear when SST equilibrates. In simulations here, cloud radiative feedbacks, surface heat fluxes induced by teleconnected wind anomalies, and surface fluxes induced by QE-mediated temperature anomalies are significant disequilibrium contributors. At time scales of several months or longer, remaining Atlantic ITCZ rainfall reductions are maintained by the upped-ante mechanism.
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 | 0,000 | 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) | 0,000 | 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 ».