Contribution of stratospheric warmings to temperature trends in the middle atmosphere from the lidar series obtained at Haute-Provence Observatory (44°N)

International audienceThis study describes a method to calculate long-term temperature trends, as an alternative to the ones based on monthly mean temperatures, which are highly impacted by the high winter variability partially due to wave-mean flow interactions like Sudden Stratospheric Warmings (SSW). This method avoids the strong influence of SSWs and provides "background" temperature trend estimates which are in better agreement with expected direct radiative effects. The data set used results from lidar measurements - performed above southern France continuously since late 1978 - combined with radiosonde profiles. With this new methodology, the long-term trends during winter at 40 km shows a larger cooling per decade (−2 ± 0.4 K) than when the mean temperature is used (−0.4 ± 0.4 K). The background temperature trend is closer to the summer trend estimates which are similar whatever the temperature proxy used, due to the absence of SSWs (−2.9 ± 0.3 K per decade with the mean-based method and −3.4 ± 0.3 K per decade with the background-based calculation). Based on this background temperature, composite evolutions of winter anomalies for both vortex-displacement and vortex-splitting major SSWs have been displayed: in both cases the largest warming occurs at the time of the SSW in the upper stratosphere, with mean amplitudes of more than 10 K. A warm signal in the upper mesosphere could suggest a potential precursory role of gravity waves. Displacement-type events present an 18-day periodicity, which is a clear sign of the wave number one Rossby wave. Colder tropospheric temperatures are noticed before and during the SSW, and warmer ones after the event, with a stronger signal for split-type events

Multiple symptoms of total ozone recovery inside the Antarctic vortex during austral spring

The long-term evolution of total ozone column inside the Antarctic polar vortex is investigated over the 1980-2016 period. Trend analyses are performed using a multilinear regression (MLR) model based on various proxies (heat flux, QBO, solar flux, AAO and aerosols). Annual total ozone column corresponding to the mean monthly values inside the vortex in September and during the period of maximum ozone depletion from September 15th to October 15th are used. Total ozone columns from combined TOMS-N7, SBUV-N9, TOMS-EP and OMI-TOMS satellite datasets and the Multi-Sensor Reanalysis (MRS-2) dataset are considered in the study. Ozone trends are computed by a piecewise trend model (PWT) before and after the turnaround in 2001. In order to evaluate total ozone within the vortex, two classification methods are used, based on the potential vorticity gradient as a function of equivalent latitude. The first standard one, considers this gradient at a single isentropic level (475K or 550K), while the second one uses a range of isentropic levels between 400K and 600K. The regression model includes a new proxy that represents the stability of the vortex during the studied month period. The determination coefficient (R2) between observations and modeled values increases by ~0.05 when this proxy is included in the MLR model. The higher R2 (0.93-0.95) and the minimum residuals are found for the second classification method in the case of both datasets and months periods. Trends in September are statistically significant at 2 sigma level with values ranging between 1.85 and 2.67 DU yr-1 depending on the methods and data sets. This result confirms the recent studies of Antarctic ozone healing during that month. Trends after 2001 are 2 to 3 times lower than before the turnaround year as expected from the response to the slowly ODS decrease in Polar regions.Estimated trends in the 15Sept-15Oct period are smaller than in September. They vary from 1.15 to 1.78 DU yr-1 and are hardly significant at 2 level. Ozone recovery is also confirmed by a steady decrease of the relative area of total ozone values lower than 150 DU within the vortex in the 15Sept-15Oct period since 2010. Comparison of the evolution of the ozone hole area in September and October show a decrease in September, confirming the later formation of the ozone hole during that month.Fil: Pazmino, Andrea. Universidad Paris Saclay; FranciaFil: Godin Beekmann, Sophie. Universidad Paris Saclay; FranciaFil: Hauchecorne, Alain. Universidad Paris Saclay; FranciaFil: Claud, Chantal. Ecole Polytechnique; FranciaFil: Khaykin, Sergey. Universidad Paris Saclay; FranciaFil: Goutail, Florence. Universidad Paris Saclay; FranciaFil: Wolfram, Elian Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Ministerio de Defensa; ArgentinaFil: Salvador, Jacobo Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Ministerio de Defensa; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Universidad Nacional de la Patagonia Austral; ArgentinaFil: Quel, Eduardo Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina. Ministerio de Defensa; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentin

PICARD payload thermal control system and general impact of the space environment on astronomical observations

International audiencePICARD is a spacecraft dedicated to the simultaneous measurement of the absolute total and spectral solar irradiance, the diameter, the solar shape, and to probing the Sun's interior by the helioseismology method. The mission has two scientific objectives, which are the study of the origin of the solar variability, and the study of the relations between the Sun and the Earth's climate. The spacecraft was successfully launched, on June 15, 2010 on a DNEPR-1 launcher. PICARD spacecraft uses the MYRIADE family platform, developed by CNES to use as much as possible common equipment units. This platform was designed for a total mass of about 130 kg at launch. This paper focuses on the design and testing of the TCS (Thermal Control System) and in-orbit performance of the payload, which mainly consists in two absolute radiometers measuring the total solar irradiance, a photometer measuring the spectral solar irradiance, a bolometer, and an imaging telescope to determine the solar diameter and asphericity. Thermal control of the payload is fundamental. The telescope of the PICARD mission is the most critical instrument. To provide a stable measurement of the solar diameter over three years duration of mission, telescope mechanical stability has to be excellent intrinsically, and thermally controlled. Current and future space telescope missions require ever-more dimensionally stable structures. The main scientific performance related difficulty was to ensure the thermal stability of the instruments. Space is a harsh environment for optics with many physical interactions leading to potentially severe degradation of optical performance. Thermal control surfaces, and payload optics are exposed to space environmental effects including contamination, atomic oxygen, ultraviolet radiation, and vacuum temperature cycling. Environmental effects on the performance of the payload will be discussed. Telescopes are placed on spacecraft to avoid the effects of the Earth atmosphere on astronomical observations (turbulence, extinction, ...). Atmospheric effects, however, may subsist when spacecraft are launched into low orbits, with mean altitudes of the order of 735 km

Helioseismology with PICARD

PICARD is a CNES micro-satellite launched in June 2010 (Thuillier at al. 2006). Its main goal is to measure the solar shape, total and spectral irradiance during the ascending phase of the activity cycle. The SODISM telescope onboard PICARD also allows us to conduct a program for helioseismology in intensity at 535.7 nm (Corbard et al. 2008). One-minute cadence low-resolution full images are available for a so-called medium-$l$ program, and high-resolution images of the limb recorded every 2 minutes are used to study mode amplification near the limb in the perspective of g-mode search. First analyses and results from these two programs are presented here.Comment: 6 pages, 6 figures, Eclipse on the Coral Sea: Cycle 24 Ascending, GONG 2012 / LWS/SDO-5 / SOHO 27, November 12 - 16, 2012, Palm Cove, Queensland. Accepted for publication in Journal of Physics Conference Series on March 1st 201

Autonomies of Art and Culture

This dossier aims to explore the way social sciences study relations between spaces of symbolic production and the political or economic fields. It focuses on uses in the sociology of culture, art, and ideas of the concept of autonomy, and on the various forms that the relative autonomy of art and culture can take depending on the configurations studied. The contributions and different case studies presented highlight the polysemy of the concept of autonomy on a theoretical level, and the multiplicity of its variations on an empirical level. Through a comparative presentation of the different cases studied in the dossier, the introduction specifically addresses three issues: the links between scholarly and vernacular uses of the concept of autonomy ; the empirical measure of the latter ; and the social conditions that enable it.Ce dossier entend revenir sur la manière dont les sciences sociales étudient les rapports entre les espaces de production symboliques et les champs politique ou économique. Il se centre sur les usages en sociologie de la culture, de l’art et des idées du concept d’autonomie, et sur les diverses formes que cette autonomie relative des arts et de la culture peut prendre selon les configurations étudiées. Les contributions au dossier et les différentes études de cas présentées mettent en évidence la polysémie du concept d’autonomie sur le plan théorique, et la multiplicité de ses déclinaisons au niveau empirique. À travers une présentation comparée des différents cas étudiés dans le dossier, l’introduction aborde plus particulièrement trois questions: l’articulation entre les usages savants et indigènes du concept d’autonomie, la mesure empirique de l’autonomie et ses conditions sociales de possibilité.Este dossier pretende reconsiderar la manera como las ciencias sociales estudian las relaciones entre los espacios de producción simbólicos y el campo político y económico. Se centra en el uso del concepto de autonomía en la sociología de la cultura, del arte y de las ideas, y sobre las diferentes formas que esta autonomía relativa del arte y la cultura, puede adoptar según las configuraciones estudiadas. Los artículos que componen este dossier y los diferentes estudios de caso presentados muestran la polisemia del concepto de autonomía, en el plano teórico así como la multiplicidad de sus formas a nivel empírico. A través de una presentación comparada de los diferentes casos que componen el dossier, la introducción aborda en espacial tres puntos: la articulación entre los usos expertos y profanos del concepto de autonomía, la medida en que dicha autonomía se constata a nivel empírico y sus condiciones sociales de posibilidad

Autonomies des arts et de la culture

Ce dossier entend revenir sur la manière dont les sciences sociales étudient les rapports entre les espaces de production symboliques et les champs politique ou économique. Il se centre sur les usages en sociologie de la culture, de l’art et des idées du concept d’autonomie, et sur les diverses formes que cette autonomie relative des arts et de la culture peut prendre selon les configurations étudiées. Les contributions au dossier et les différentes études de cas présentées mettent en évidence la polysémie du concept d’autonomie sur le plan théorique, et la multiplicité de ses déclinaisons au niveau empirique. À travers une présentation comparée des différents cas étudiés dans le dossier, l’introduction aborde plus particulièrement trois questions : l’articulation entre les usages savants et indigènes du concept d’autonomie, la mesure empirique de l’autonomie et ses conditions sociales de possibilité.This dossier aims to explore the way social sciences study relations between spaces of symbolic production and the political or economic fields. It focuses on uses in the sociology of culture, art, and ideas of the concept of autonomy, and on the various forms that the relative autonomy of art and culture can take depending on the configurations studied. The contributions and different case studies presented highlight the polysemy of the concept of autonomy on a theoretical level, and the multiplicity of its variations on an empirical level. Through a comparative presentation of the different cases studied in the dossier, the introduction specifically addresses three issues : the links between scholarly and vernacular uses of the concept of autonomy ; the empirical measure of the latter ; and the social conditions that enable it.Este dossier pretende reconsiderar la manera como las ciencias sociales estudian las relaciones entre los espacios de producción simbólicos y el campo político y económico. Se centra en el uso del concepto de autonomía en la sociología de la cultura, del arte y de las ideas, y sobre las diferentes formas que esta autonomía relativa del arte y la cultura, puede adoptar según las configuraciones estudiadas. Los artículos que componen este dossier y los diferentes estudios de caso presentados muestran la polisemia del concepto de autonomía, en el plano teórico así como la multiplicidad de sus formas a nivel empírico. A través de una presentación comparada de los diferentes casos que componen el dossier, la introducción aborda en espacial tres puntos : la articulación entre los usos expertos y profanos del concepto de autonomía, la medida en que dicha autonomía se constata a nivel empírico y sus condiciones sociales de posibilidad

Charlemagne et Agoulant: la dualité du monde dans la chanson d'Aspremont

La chanson de geste Aspremont présente les prouesses de l’armée carolingienne face à l’attaque acharnée des troupes païennes. La structure féodale européenne se voit terriblement menacée par l’insolence d’une nation criminelle qui cherche à exterminer la chrétienté et à soumettre ses adeptes. Les poètes du XIIe siècle, à la merci de l’Église, s’engagent à comparer les deux types de héros épique qui luttent sur le champ de bataille. Et ce sera évidemment l’armée de l’empereur Charlemagne qui vaincra face aux troupes du roi Agoulant d’Afrique. Le jongleur récite cette chanson afin de convaincre son auditoire. Malgré l’intérêt suscité envers l’Autre, les gens du Moyen Âge devaient penser qu’il s’agissait d’une race d’infidèles qui avait abjuré la loi chrétienne en faveur d’une divinité démoniaque qui tentait d’anéantir la religion qui embrasse Dieu. Quasiment tout est obscur, voire ténébreux, chez le païen. L’étude des portraits physiques et moraux du païen et du chrétien, leurs différentes origines géographiques et notamment la dissimilitude existante à l’égard des deux religions qui s’opposent sur le champ de bataille permettront de discerner la discrimination dont le personnage sarrasin souffre. Les auteurs médiévaux créent une sorte de stéréotype sarrasin dans le but de corrompre son image au sein de la société chrétienne et d’inciter ainsi à la haine raciale et religieuse envers celui qui ne croit pas en Dieu. La chrétienté doit impérativement sortir victorieuse de cet affrontement belliqueux qu’est la bataille d’Aspremont. Elle tient à s’imposer en tant que religion dominante par rapport au reste. Pour obtenir le triomphe, les chevaliers de l’armée de Charlemagne devront professer un amour inébranlable envers Dieu et Lui devra leur accorder la plus belle des récompenses : si le guerrier meurt sur le champ de bataille après avoir prouvé l’amour qu’il ressent pour Dieu, on lui permettra d’aller au paradis. Le chevalier chrétien devient ainsi donc un martyr qui acceptera de mourir pour défendre sa religion