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Cette thèse est basée sur des simulations numériques régionales et aborde, d’un point de vue énergétique, la variabilité à Méso (O(10-100)km) et Sous-mésoéchelle (O(0.1-10)km) dans la région du Courant des Aiguilles.(i) La variabilité de sous-mésoéchelle à la transition entre les deux branches du Courant des Aiguilles (28◦E-26◦E) est dominée, en l’absence de méandres de mésoéchelle, par des tourbillons cycloniques frontaux formant un ‘vortex street’. La tension ambiante frontogénétique intensifie le cisaillement frontal qui déclenche l’instabilité barotrope menant à la génération de tourbillons de sous-mésoéchelle.(ii) Un budget modal d’Energie Cinétique des Tourbillons est développé pour caractériser les transferts d’énergie entre les différentes structures verticales. Les interactions canalisées par la topographie (3 processus) résultent globalement en une perte d’énergie pour les tourbillons de mésoéchelle plus grande que les processus de dissipation (friction au fond et vent) et une cascade verticale inverse (interactions triadiques) renforce les tourbillons de mésoéchelle dans les zones au large.(iii) Notre budget modal permet de caractériser la région du Courant des Aiguilles comme une source nette d’énergie pour les tourbillons de mésoéchelle en contradiction avec celui estimé à partir de données d’altimétrie. Cette différence vient des données d’altimétrie ne tenant pas compte de la contribution principale de la dynamique aux sources et puits d’énergie des tourbillons de mésoéchelle (partie linéaire de la dynamique agéostrophique du mode barotrope et du 1er mode barocline). This dissertation is based on regional numerical simulations and addresses, from an energetic perspective, the Meso (O(10-100)km) and Submesoscale (O(0.1- 10)km) variability in the Agulhas Current region.(i) Submesoscale variability at the transition between the two Agulhas Current branches (28◦E-26◦E) is dominated, in the absence of mesoscale meanders, by cyclonic frontal eddies forming a ’vortex street’. The frontogenetic background strain intensifies the frontal shear which triggers the barotropic instability leading to submesoscale eddies generation.(ii) A modal Eddy Kinetic Energy budget is derived to characterize the energy transfers between the different vertical structures. Interactions canalized by topography (3 processes) globally result in a larger energy loss for mesoscale eddies than dissipation processes (bottom friction and wind) and an inverse vertical cascade (triadic interactions) reinforces mesoscale eddies in offshore areas.(iii) Our modal budget allows to characterize the Agulhas Current region as a net energy source for mesoscale eddies in contradiction with one inferred from altimetry data. The discrepancies come from altimetry data not accounting for the main contribution of the dynamics to mesoscale eddies energy sources and sinks (ageostrophic linear part of the dynamics of the barotropic and 1st baroclinic modes).

In the present study, we explored the temperature evolution and hydrogen desorption properties of the Mg50Ni50 alloy through both numerical simulation and experimental analyses. Desorption kinetics characterization was carried out using the volumetric method, specifically employing a Sievert's-type apparatus to investigate solid-gas reactions. The experiments covered a temperature range from 313 K to 353 K, with an initial hydrogen pressure of 12 bar. Simultaneously, a mathematical approach was employed to numerically investigate the temperature evolution within the hydride bed. Using COMSOL Multiphysics as a simulator, a numerical simulation was conducted based on experimental data. The study examined the impact of cooling temperature on hydride temperature evolution. Results revealed that hydrogen desorption kinetics of the amorphous Mg50Ni50 alloy are more significant compared to those of Mg2Ni compounds. Moreover, the effect of the warming temperature on the equilibrium pressure can also be observed in the hydrogen desorption isotherm curves. The experimental study of the Mg50Ni50 alloy provided activation energy data, along with determination of hydride formation enthalpy and entropy. On the other hand, we showed that the hydride temperature is maximum at the hydride-hydrogen interface within the hydride center.

FAERE Working Paper, 2019.23 ; While environmental values are spreading among societies, theyhardly lead to effective political actions. This may be due to an overestimation of the sharing of those values among people, or to a lack ofpolitical power of environmentalists vis-à-vis materialist citizens. Wepropose a theoretical model to investigate these two channels, based ona setup a la Grossman and Helpman (1994), in which lobby is a strategy available to social groups, in order to influence the government onenvironmental taxes. Because societies have being historically markedby materialist habits, citizens sharing those habits face lower costswhen getting organized. By considering endogenous lobby formation ala Mitra (1999), we show that, in order for environmental and materialist lobbies to coexist, the society must be mixed enough. Based on adynamic framework a la Besley and Persson (2019), we investigate howsocial values change over time. Whenever lobbying by materialists prevails, a unique social equilibrium exists, featuring a stable hegemonyby materialist values. If environmentalists get organized too, a secondsocial equilibrium emerges, that is locally stable and more favorableto them. However, the threshold might be very high, above which thecultural transition effectively takes off. By calibrating the model, westudy counter-acting forces allowing to improve the odds of the environmental transition, such as cultural mutations, social-signaling, andlowering organizational costs. Finally, we provide policy implications. ; Alors que les valeurs environnementales se répandent dans les sociétés, elles ne débouchent guère sur des actions politiques efficaces. Cela peut être dû à une surestimation du partage de ces valeurs entre les gens, ou à un manque de pouvoir politique des écologistes vis-à-vis des citoyens matérialistes. Nous proposons un modèle théorique pour investiguer ces deux canaux, basé sur un cadre à la Grossman et Helpman (1994), dans lequel le lobbying est une stratégie à la disposition des ...

This deliverable includes the methodology in EnergyPROSPECTS for an in-depth study of energy citizenship. It features the criteria used for selecting the cases for indepth study, the list of cases selected for in-depth study as well as key research foci and empirical research questions.

The rapidly changing climate presents unprecedented challenges, especially in permafrost regions, where its thawing directly affects houses, mines, roads, pipelines, airport runways, and rail tracks. Monitoring the dynamics of ground ice in permafrost landscapes is essential for assessing geohazards and adapting infrastructure to changing conditions. This abstract presents a new initiative utilizing cosmic neutrons metrology for permafrost studies, specifically focusing on ground-ice content monitoring. Traditional methods for assessing ground-ice content in permafrost regions involve labor-intensive surveys and analysis of geomorphological features. However, these approaches are often limited in spatial coverage and may not capture the full extent of ground-ice distribution. In response to these challenges, we propose leveraging cosmic neutrons as a non-invasive and scalable method for assessing ground-ice content. Cosmic neutrons naturally penetrate the Earth's surface and interact with hydrogen atoms in the soil, including those bound in water molecules. By measuring the cosmic neutron albedo, which is the flux of epithermal neutrons that are partially thermalized in the ground, we can infer the presence and distribution of ground ice. This approach builds upon established techniques used for soil moisture monitoring, adapting them for permafrost studies. In that regard, we conducted Monte Carlo simulations of cosmic neutron transport and interaction with modeled ground to investigate the feasibility of using cosmic neutrons for ground-ice content monitoring. Our simulations considered various ground compositions and ice concentrations to assess the sensitivity of cosmic neutron measurements to ground-ice content. The results of our simulations provide promising proof-of-concept for the proposed method, demonstrating its potential for accurately estimating ground-ice content in permafrost landscapes. Additionally, we are developing at DOSEO (CEA – Saclay, France) thermal over fast neutron reference fields that could be used to test, characterize, and calibrate detectors specifically for the presented application. The proposed method offers several advantages. Firstly, it provides measurements on a metric scale (~10m wide on ~1m depth), effectively balancing local detail with regional coverage, thus making it well-suited for mapping geohazards on a kilometric scale. Additionally, cosmic neutrons albedo measurements is non-destructive and non-invasive and can be applied across diverse permafrost landscapes, offering valuable insights into ground-ice dynamics. Moreover, mapping ground-ice content is feasible through the flexible deployment of neutron detectors. These detectors can either be moved around the study area to gather spatially distributed measurements or installed as fixed monitoring stations, enabling continuous observation of ground-ice dynamics across different seasons and over time. Integration of data from cosmic neutrons albedo measurements into Geographic Information System (GIS) applications enhances the ability to map geohazards and predict future changes in permafrost landscape stability. By combining information on ground-ice content with elevation, drainage patterns, periglacial features, and infrastructure, a better understanding of the interactions between climate change and geohazards in permafrost regions is achievable.In conclusion, cosmic neutrons metrology offers a promising approach for monitoring ground-ice content in permafrost landscapes. By advancing our understanding of permafrost dynamics, this initiative contributes to the broader goals of cryosphere monitoring and sustainable development.

AbstractEuropean climate is associated with variability and changes in the mid-latitude atmospheric circulation. In this study, we aim to investigate potential future change in circulation over Europe by using the EURO-CORDEX regional climate projections at 0.11° grid mesh. In particular, we analyze future change in 500-hPa geopotential height (Gph), 500-hPa wind speed and mean sea level pressure (MSLP) addressing different warming levels of 1 °C, 2 °C and 3 °C, respectively. Simple scaling with the global mean temperature change is applied to the regional climate projections for monthly mean 500-hPa Gph and 500-hPa wind speed. Results from the ensemble mean of individual models show a robust increase in 500-hPa Gph and MSLP in winter over Mediterranean and Central Europe, indicating an intensification of anticyclonic circulation. This circulation change emerges robustly in most simulations within the coming decade. There are also enhanced westerlies which transport warm and moist air to the Mediterranean and Central Europe in winter and spring. It is also clear that, models showing different responses to circulation depend very much on the global climate model ensemble member in which they are nested. For all seasons, particularly autumn, the ensemble mean is much more correlated with the end of the century than most of the individual models. In general, the emergence of a scaled pattern appears rather quickly.

Les conséquences du changement climatique sont particulièrement aiguës au Kenya, où 80 % des terres sont arides ou semi-arides. Quelle perspective critique et constructive le concept d’habitabilité peut-il offrir dans ce contexte ? Fondé sur un travail de terrain réalisé au Kenya en 2022 et 2023, cet article entend affiner une définition in situ de l’habitabilité, en utilisant exclusivement des données qualitatives issues de deux phases de recherche, complétées par des exercices de vidéo-cartographie. Loin de proposer une lecture positiviste de l’habitabilité, portée par une conception exclusivement mécanique et linéaire des dynamiques de mobilité, cette étude propose de mieux relier l’habitabilité aux pratiques quotidiennes, aux habitudes, aux solidarités, voire aux résistances qui constituent la vie ordinaire des habitants des communautés et des personnes déplacées. L’habitabilité se situerait alors au cœur de l’intrication entre socialité et spatialité, entre social et biologique, qui définit – selon Stanley Cavell – la forme de vie humaine. The consequences of climate change are particularly acute in Kenya, where 80% of the land is arid or semi-arid. What critical and constructive perspective can the concept of habitability offer in this context? Based on fieldwork carried out in Kenya in 2022 and 2023, this article aims to refine an in-situ definition of habitability, using exclusively qualitative data from two research phases, supplemented by video-mapping exercises. Far from proposing a positivist reading of habitability, driven by an exclusively mechanical and linear conception of mobility dynamics, this study proposes to better link habitability to the daily practices, habits, solidarities and even resistances that make up the ordinary lives of community dwellers and displaced persons. Habitability would then lie at the heart of the intricacy between sociality and spatiality, between the social and the biological, which defines – according to Stanley Cavell – “the human form of life.”

Energy management within microgrids under the presence of large number of renewables such as photovoltaics is complicated due to uncertainties involved. Randomness in energy production and consumption make both the prediction and optimality of exchanges challenging. In this paper, we evaluate the impact of uncertainties on optimality of different robust energy exchange strategies. To address the problem, we present AIROBE, a data-driven system that uses machine-learning-based predictions of energy supply and demand as input to calculate robust energy exchange schedules using a multiband robust optimization approach to protect from deviations. AIROBE allows the decision maker to tradeoff robustness with stability of the system and energy costs. Our evaluation shows, how AIROBE can deal effectively with asymmetric deviations and how better prediction methods can reduce both the operational cost while at the same time may lead to increased operational stability of the system.