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Defining Mesoscale Eddies Boundaries From In-Situ Data and a Theoretical Framework
No full textInternational audienceMesoscale eddies play an important role in transporting water properties, enhancing air-sea interactions, and promoting large-scale mixing of the ocean. They are generally referred to as "coherent" structures because they are organized, rotating fluid elements that propagate within the ocean and have long lifetimes (months or even years). Eddies have been sampled by sparse in-situ vertical profiles, but because in-situ ocean observations are limited, they have been characterized primarily from satellite observations, numerical simulations, or relatively idealized geophysical fluid dynamics methods. However, each of these approaches has its limitations. Many questions about the general structure and "coherence" of ocean eddies remain unanswered. In this study, we investigate the properties of seven mesoscale eddies sampled with relative accuracy during four different field experiments in the Atlantic. Our results suggest that the Ertel Potential Vorticity (EPV) is a suitable parameter to isolate and characterize the eddy cores and their boundaries. The latter appear as regions of finite horizontal extent, characterized by a local extremum of the vertical and horizontal components of the EPV. These are found to be closely related to the presence of a different water mass in the core (relative to the background) and the steepening of the isopycnals due to eddy occurrence and dynamics. Based on these results, we propose a new criterion for defining eddies at the mesoscale. We test our approach using a theoretical framework and explore the possible magnitude of this new criterion, including its upper bound
Abundant hydrocarbons in the disk around a very-low-mass star
No full textInternational audienceVery-low-mass stars (those less than 0.3 solar masses) host orbiting terrestrial planets more frequently than other types of stars. The compositions of those planets are largely unknown but are expected to relate to the protoplanetary disk in which they form. We used James Webb Space Telescope mid-infrared spectroscopy to investigate the chemical composition of the planet-forming disk around ISO-ChaI 147, a 0.11-solar-mass star. The inner disk has a carbon-rich chemistry; we identified emission from 13 carbon-bearing molecules, including ethane and benzene. The high column densities of hydrocarbons indicate that the observations probe deep into the disk. The high carbon-to-oxygen ratio indicates radial transport of material within the disk, which we predict would affect the bulk composition of any planets forming in the disk
A new insight into monsoon intraseasonal variability as revealed from distinct wind-precipitation regimes over the southwest coast of India
No full textInternational audienceThis study evaluates the observed non-linearity in the wind-precipitation relationship over India's southwest coast and maps this non-linearity to monsoon intraseasonal oscillations. The wind-precipitation data is subjected to clustering, and five distinct regimes are identified. The large-scale dynamical and thermodynamical condition that leads to wind-precipitation clustering is explored. It uses novel observations from the Stratosphere-Troposphere wind profiler radar placed over Cochin (10.04° N; 76.33° E) for the period 2019-2021 to derive characteristics of monsoon low-level jets. Out of five wind-precipitation clusters, low wind low precipitation (LWLP) and low wind high precipitation clusters (LWHP) bear signatures of monsoon break conditions over central India. The occurrence of Madden Julian events or monsoon lows in LWHP generates heavy rainfall over the southwest coast. The high wind low precipitation (HWLP) cluster occurs during the weak phase of northward propagating monsoon intraseasonal oscillation (MISO) over the southwest coast, while the high wind high precipitation (HWHP) cluster lies within the strong phase of MISO. The fifth cluster, the high wind extreme precipitation cluster (HWEP), although technically lying within the strong phase of MISO, however has more apparent signatures of northwestward propagating monsoon depressions. The Lagrangian trajectories launched from 500 hPa level for each cluster reveal some intriguing aspects. The dry air intrusion from adjacent regions near the west coast makes the mid-troposphere dry over the southwest coast in LWLP and HWLP clusters. In HWHP and HWEP, strong moisture sources confined over the west coast create mid-troposphere moistening owing to the moisture supply from below 500 hPa. This study highlights that wind-precipitation clustering effectively defines sub-seasonal variability during the monsoon
Détection de similarités sémantiques ou structurelles pour la comparaison de pièces de théâtre
No full textInternational audienceFrom the very beginnings of modern theater in France, dramatic creation has been using several practices of imitation and adaptation of earlier texts, from biblical, antique or historical sources. Here, we focus on plays inspired by other plays, and on ways of automatically detecting similarities between the texts of such plays. We present approaches based on structural similarities and others based on semantic similarities between play texts, using word embedding methods. Finally, we look at the advantages of developing hybrid approaches that combine these two criteria, using on the one hand the corpus of sources on dramatic creation provided on the Hyperpièces website for comedies, tragi-comedies and tragedies published in France from 1550 to 1650, and on the other hand the Dracor corpus.Dès les débuts du théâtre moderne en France, la création dramatique s’est nourrie de plusieurs pratiques d’imitation ou d’adaptation de textes antérieurs, de sources bibliques, antiques ou historiques. Nous nous intéressons ici aux pièces inspirées par d’autres pièces de théâtre, et aux moyens de détecter automatiquement les similarités entre les textes des pièces dans ce cas. Nous présenterons des approches fondées sur des similarités de structure et d’autres fondées sur des similarités sémantiques entre les textes des pièces, en utilisant des méthodes de plongements de mots. Enfin, nous étudierons l’intérêt de développer des approches hybrides qui mêlent ces deux critères, en mobilisant d’une part le corpus des sources de la création dramatique fournies sur le site Hyperpièces à propos des comédies, tragi-comédies et tragédies publiées en France de 1550 à 1650, et d’autre part le corpus Dracor
Méthode des éléments finis. Preuves détaillées en vue d'une formalisation en Coq
No full textTo obtain the highest confidence on the correction of numerical simulation programs for the resolution of Partial Differential Equations (PDEs), one has to formalize the mathematical notions and results that allow to establish the soundness of the approach. The finite element method is one of the popular tools for the numerical resolution of a wide range of PDEs. The purpose of this document is to provide the formal proof community with very detailed pen-and-paper proofs for the construction of the Lagrange finite elements of any degree on simplices in positive dimension.Pour obtenir la plus grande confiance dans l'exactitude des résultats de programmes de simulation numérique pour la résolution d'Équations aux Dérivées Partielles (EDPs), il faut formaliser les notions mathématiques sur lesquelles ils sont basés. La méthode des éléments finis est l'un des outils les plus utilisés pour la résolution de larges gammes d'EDPs. L'objectif de ce document est de fournir à la communauté des chercheurs en preuve formelle des preuves papiers très détaillées pour la construction des éléments finis de Lagrange de tout degré sur des simplexes en dimension quelconque
The Value of Leisure Synchronization
No full textInternational audienceThis paper explores the extent to which workers are willing to trade hours worked for leisure time shared with their spouse. We use the fact that the number and timing of paid vacation days to which French employees are entitled vary in a quasi-random way from year to year along with the dates of public holidays. Self-employed workers do not benefit from public holidays, but we show that a large fraction of them substitute a day of unpaid leisure for a day of paid work whenever their spouse gets an extra day of paid leave
Multistage stochastic optimization of a mono-site hydrogen infrastructure by decomposition techniques
No full textInternational audienceThe development of hydrogen infrastructures requires to reduce their costs. In this paper, we develop a multistage stochastic optimization model for the management of a hydrogen infrastructure which consists of an electrolyser, a compressor and a storage to serve a transportation demand. This infrastructure is powered by three different sources: on-site photovoltaic panels (PV), renewable energy through a power purchase agreement (PPA) and the power grid. We consider uncertainties affecting on-site photovoltaic production and hydrogen demand. Renewable energy sources are emphasized in the hydrogen production process to ensure eligibility for a subsidy, which is awarded if the proportion of nonrenewable electricity usage stays under a predetermined threshold. We solve the multistage stochastic optimization problem using a decomposition method based on Lagrange duality. The numerical results indicate that the solution to this problem, formulated as a policy, achieves a small duality gap, thus proving the effectiveness of this approach
Distribution spatio-temporelle de la matière et des molécules organiques dans les sédiments du réseau d'assainissement de la Ville de Paris. Lien avec les pratiques et usages durant l'Anthropocène
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Distribution spatio-temporelle de la matière organique et des molécules dans les sédiments du réseau d'assainissement de la ville de Paris. Lien avec les pratiques et usages au cours de l'Anthropocène par une approche multi-proxy.
No full textInternational audienceHighlights-Delineation of the sewershed of silt trap to be able to precisely trace the sources of particles.- Comparison of pharmaceutical products recorded in sediment and consumer populations.- Spatial and temporal distribution of pharmaceuticals in Paris sewer sediments
Radiative-convective models of the atmospheres of Uranus and Neptune: heating sources and seasonal effects
No full textInternational audienceThe observations made during the Voyager 2 yby have shown that the stratosphere of Uranus and that of Neptune are warmer than expected by previous models. In addition, no seasonal variability of the thermal structure has been observed on Uranus since Voyager 2 era and signi cant subseasonal variations have been revealed on Neptune.Aims. In this paper, we evaluate different realistic heat sources that can induce suf cient heating to warm the atmosphere of these planets and we estimate the seasonal effects on the thermal structure.Methods. The seasonal radiative-convective model developed by the Laboratoire de Météorologie Dynamique was used to reproduce the thermal structure of these planets. Three hypotheses for the heating sources were explored separately: aerosol layers, a higher methane mole fraction, and thermospheric conduction.Results. Our modelling indicates that aerosols with plausible scattering properties can produce the requisite heating for Uranus, but not for Neptune. Alternatively, greater stratospheric methane abundances can provide the missing heating on both planets, but the large values needed are inconsistent with current observational constraints. In contrast, adding thermospheric conduction cannot warm the stratosphere of both planets alone. The combination of these heat sources is also investigated. In the upper troposphere of both planets, the meridional thermal structures produced by our model are found inconsistent with those retrieved from Voyager 2/IRIS data. Furthermore, our models predict seasonal variations should exist within the stratospheres of both planets while observations showed that Uranus seems to be invariant to meridional contrasts and only subseasonal temperature trends are visible on Neptune. However, a warm south pole is seen in our simulations of Neptune as observed since 2003