Evidence for a k^{-5/3} spectrum from the EOLE Lagrangian balloons in the low stratosphere

The EOLE Experiment is revisited to study turbulent processes in the lower stratosphere circulation from a Lagrangian viewpoint and resolve a discrepancy on the slope of the atmospheric energy spectrum between the work of Morel and Larcheveque (1974) and recent studies using aircraft data. Relative dispersion of balloon pairs is studied by calculating the Finite Scale Lyapunov Exponent, an exit time-based technique which is particularly efficient in cases where processes with different spatial scales are interfering. Our main result is to reconciliate the EOLE dataset with recent studies supporting a k^{-5/3} energy spectrum in the range 100-1000 km. Our results also show exponential separation at smaller scale, with characteristic time of order 1 day, and agree with the standard diffusion of about 10^7 m^2/s at large scales. A still open question is the origin of a k^{-5/3} spectrum in the mesoscale range, between 100 and 1000 km.Comment: 19 pages, 1 table + 5 (pdf) figure

Violence ou douceur. Les normes éducatives dans les sociétés grecque et romaine

La violence était omniprésente dans le cadre des institutions éducatives du monde antique grec et latin. Elle s’exerçait à la fois contre les usagers de l’école et du gymnase, entre ces usagers, et contre les maîtres. L’étude s’interroge sur la violence institutionnelle autorisée par la loi ou la coutume et la violence réprimée, sur les formes et l’expression de cette violence, et sur les évolutions, de la naissance de l’école à l’âge classique, au Ve siècle avant notre ère, à la fin de l’Antiquité. L’introduction de la douceur dans les rapports pédagogiques, dont le théoricien majeur est Quintilien, est tardive. Ces pratiques violentes faisaient de toute évidence écho à la violence diffuse qui affectait la vie des Grecs et des Romains. Le gymnase et l’école dans les mondes grec et romain étaient à la fois un reflet et une propédeutique de la vie sociale dans l’Antiquité gréco-romaine.Violence was omnipresent in the educational institutions of the Ancient Latin and Greek world. It was employed against the users of school and gymnasium, between those users and against the masters. This study investigates institutional violence authorized by law or custom and the violence that was repressed, the forms and expression of this violence, and the evolutions between the birth of the school in the classical period, in the 5th century BC, to the end of Antiquity. The introduction of gentleness in teaching relationships, of which Quintilianus is the major theoretician, was late. Obviously, these violent practices were the echo of the diffuse violence which affected the lives of Greeks and Romans. In the Roman and Greek worlds, the school and gymnasium were both a reflection of and an initiation into the social life of Greek and Roman Antiquity. (Traduction Nigel Briggs)In den Bildungseinrichtungen der antiken Welt war Gewalt allgegenwärtig; sie richtete sich dort sowohl gegen die Besucher von Schulen und Stadien als auch gegen deren Lehrer und kam außerdem zwischen den Schülern zum Ausdruck. Der Beitrag befasst sich sowohl mit den durch Recht und Gewohnheit zugelassenen als auch mit den sanktionierten Formen von Gewalt und analysiert deren Ausdrucksformen in chronologischen Schnitten, von der Schule der klassischen Zeit im 5. Jahrhundert v. Chr. bis in die Spätantike. Sanftere Erziehungsformen setzten sich erst relativ spät durch; erst Quintilian lieferte dafür die wichtigsten theoretischen Vorgaben. Alles spricht dafür, dass die harte Erziehungspraxis nur der Refl ex einer diffusen Gewaltbereitschaft ist, die die Lebenswirklichkeit von Griechen und Römern generell charakterisierte; Stadion und Schule der griechisch-römischen Antike sind damit ein recht genaues Abbild des gesellschaftliche Lebens ihrer Zeit, auf das sie gleichzeitig vorbereiten sollten. (Traduction Gérard Bodé)La violencia estaba omnipresente en el marco de las instituciones educativas del mundo antiguo griego y latino. Se ejercía a la vez contra los usuarios de la escuela y del gimnasio, entre dichos usuarios y contra los maestros. El estudio examina la violencia institucional autorizada por la ley o la costumbre, y la violencia reprimida, las formas y la expresión de esa violencia, y las evoluciones, del nacimiento de la escuela en la edad clásica, en el sigloV antes de nuestra era, a finales de la antigüedad. La introducción de la dulzura en las relaciones pedagógicas cuyo mayor teórico es Quintiliano, es tardía. Esas prácticas violentas respondían sin duda alguna a la violencia difusa que afectaba la vida de los griegos y de los romanos. El gimnasio y la escuela en los mundos griego y romano eran a la vez un refl ejo y un curso preuniversitario de la vida social en la antigüedad greco-romana. (Traduction Nuria Serrano

Centre Louis-Gernet de recherches comparées sur les sociétés anciennes – CRCSA

Bernard Legras, maître de conférences à l’Université Paris-I Anthropologie, histoire et institutions de l’Antiquité Depuis 2005, le séminaire de recherche du Centre Louis-Gernet et les conférences du Centre Gustave-Glotz ont fusionné pour constituer un séminaire commun aux trois équipes Gernet (CNRS-EHESS), Glotz (CNRS-Paris-I-Paris-IV-EPHE) et « Phéacie » (Paris-I-Paris-VII). Le séminaire porte sur un thème choisi d’un commun accord pour deux ans, au rythme d’une douzaine de séances par an (..

La papyrologie documentaire grecque en 2005 : bilan et perspectives

La papyrologie documentaire grecque, née en 1788, s’est constituée en discipline scientifique à la fin du XIXe siècle et au début du XXe siècle. L’objet de cet article est de caractériser le tournant que vit cette discipline, encore jeune, au début du XXIe siècle. Trois faits ont profondément modifié la recherche papyrologique : l’accessibilité presque totale des corpus sur la Toile, la coopération de plus en plus étroite avec les autres disciplines des sciences de l’Antiquité (Altertumswissenschaft) et le développement de thématiques de recherche susceptibles de faire naître de nouvelles vocations.Greek documentary papyrology, born in 1788, emerged as a scientific discipline in the late XIXth and the early XXth century. The aim of this paper is to characterize this still young discipline at the turning point it is now experiencing at the beginning of the XXIth century. Three elements have deeply modified papyrological research: the access to almost all the textual corpus on the web, the increasingly close cooperation with the other fields of Altertumswissenschaft and the development of new topics and fields of inquiry able to give birth to new vocations

Lagrangian temperature and vertical velocity fluctuations due to gravity waves in the lower stratosphere

International audienceWave-induced Lagrangian fluctuations of temperature and vertical velocity in the lower stratosphere are quantified using measurements from superpressure balloons (SPBs). Observations recorded every minute along SPB flights allow the whole gravity wave spectrum to be described and provide unprecedented information on both the intrinsic frequency spectrum and the probability distribution function of wave fluctuations. The data set has been collected during two campaigns coordinated by the French Space Agency in 2010, involving 19 balloons over Antarctica and 3 in the deep tropics. In both regions, the vertical velocity distributions depart significantly from a Gaussian behavior. Knowledge on such wave fluctuations is essential for modeling microphysical processes along Lagrangian trajectories. We propose a new simple parameterization that reproduces both the non-Gaussian distribution of vertical velocities (or heating/cooling rates) and their observed intrinsic frequency spectrum

Centre Louis-Gernet de recherches comparées sur les sociétés anciennes - CLGRCSA

Stella Georgoudi et Jean-Louis Ferrary, directeurs d’études à lΈΡΗΕBernard Legras, maître de conférences à l’Université Paris-I « La normativité » Pour les deux années 2005-2006 et 2006-2007, le séminaire commun du Centre Gernet, en collaboration avec le Centre Gustave Glotz (Recherches sur les mondes hellénistique et romain, Paris-I/Paris-IV/EPHE) et l’Équipe d’accueil « Phéacie » (Paris-I/Paris-VII), porte sur la normativité dans quelques sociétés anciennes. La normativité est envisagée du ..

Centre Louis-Gernet de recherches comparées sur les sociétés anciennes - CLGRCSA

Stella Georgoudi et Jean-Louis Ferrary, directeurs d’études à lΈΡΗΕBernard Legras, maître de conférences à l’Université Paris-I « La normativité » Pour les deux années 2005-2006 et 2006-2007, le séminaire commun du Centre Gernet, en collaboration avec le Centre Gustave Glotz (Recherches sur les mondes hellénistique et romain, Paris-I/Paris-IV/EPHE) et l’Équipe d’accueil « Phéacie » (Paris-I/Paris-VII), porte sur la normativité dans quelques sociétés anciennes. La normativité est envisagée du ..

Respiratory pulse pressure variation fails to predict fluid responsiveness in acute respiratory distress syndrome

International audienceIntroduction: Fluid responsiveness prediction is of utmost interest during acute respiratory distress syndrome (ARDS), but the performance of respiratory pulse pressure variation (Δ RESP PP) has scarcely been reported. In patients with ARDS, the pathophysiology of Δ RESP PP may differ from that of healthy lungs because of low tidal volume (Vt), high respiratory rate, decreased lung and sometimes chest wall compliance, which increase alveolar and/or pleural pressure. We aimed to assess Δ RESP PP in a large ARDS population. Methods: Our study population of nonarrhythmic ARDS patients without inspiratory effort were considered responders if their cardiac output increased by >10% after 500-ml volume expansion. Results: Among the 65 included patients (26 responders), the area under the receiver-operating curve (AUC) for Δ RESP PP was 0.75 (95% confidence interval (CI 95): 0.62 to 0.85), and a best cutoff of 5% yielded positive and negative likelihood ratios of 4.8 (CI 95 : 3.6 to 6.2) and 0.32 (CI 95 : 0.1 to 0.8), respectively. Adjusting Δ RESP PP for Vt, airway driving pressure or respiratory variations in pulmonary artery occlusion pressure (ΔPAOP), a surrogate for pleural pressure variations, in 33 Swan-Ganz catheter carriers did not markedly improve its predictive performance. In patients with ΔPAOP above its median value (4 mmHg), AUC for Δ RESP PP was 1 (CI 95 : 0.73 to 1) as compared with 0.79 (CI 95 : 0.52 to 0.94) otherwise (P = 0.07). A 300-ml volume expansion induced a ≥2 mmHg increase of central venous pressure, suggesting a change in cardiac preload, in 40 patients, but none of the 28 of 40 nonresponders responded to an additional 200-ml volume expansion. Conclusions: During protective mechanical ventilation for early ARDS, partly because of insufficient changes in pleural pressure, Δ RESP PP performance was poor. Careful fluid challenges may be a safe alternative

Pollution trace gas distributions and their transport in the Asian monsoon upper troposphere and lowermost stratosphere during the StratoClim campaign 2017

We present the first high-resolution measurements of pollutant trace gases in the Asian summer monsoon upper troposphere and lowermost stratosphere (UTLS) from the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) during the StratoClim (Stratospheric and upper tropospheric processes for better climate predictions) campaign based in Kathmandu, Nepal, 2017. Measurements of peroxyacetyl nitrate (PAN), acetylene (C$_2$H$_2$), and formic acid (HCOOH) show strong local enhancements up to altitudes of 16\,km. More than 500\,pptv of PAN, more than 200\,pptv of C$_2$H$_2$, and more than 200\,pptv of HCOOH are observed. Air masses with increased volume mixing ratios of PAN and C$_2$H$_2$ at altitudes up to 18\,km, reaching to the lowermost stratosphere, were present at these altitudes for more than 10\,d, as indicated by trajectory analysis. A local minimum of HCOOH is correlated with a previously reported maximum of ammonia (NH$_3$), which suggests different washout efficiencies of these species in the same air masses. A backward trajectory analysis based on the models Alfred Wegener InsTitute LAgrangian Chemistry/Transport System (ATLAS) and TRACZILLA, using advanced techniques for detection of convective events, and starting at geolocations of GLORIA measurements with enhanced pollution trace gas concentrations, has been performed. The analysis shows that convective events along trajectories leading to GLORIA measurements with enhanced pollutants are located close to regions where satellite measurements by the Ozone Monitoring Instrument (OMI) indicate enhanced tropospheric columns of nitrogen dioxide (NO$_2$) in the days prior to the observation. A comparison to the global atmospheric models Copernicus Atmosphere Monitoring Service (CAMS) and ECHAM/MESSy Atmospheric Chemistry (EMAC) has been performed. It is shown that these models are able to reproduce large-scale structures of the pollution trace gas distributions for one part of the flight, while the other part of the flight reveals large discrepancies between models and measurement. These discrepancies possibly result from convective events that are not resolved or parameterized in the models, uncertainties in the emissions of source gases, and uncertainties in the rate constants of chemical reactions