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Atmospheric Specifications for Infrasound Studies: 1. Operational Analyses
No full textInternational audienceOperational analysis products issued by weather services are needed for the Comprehensive Nuclear-Test-Ban Treaty's (CTBT) infrasound monitoring activities. They provide atmospheric specifications as high as 80 km altitude. They are used to feed propagation simulations designed to characterize sources of interest. Acoustic waveguides for long-range infrasound propagation form in the lower and middle atmosphere between approximately 10 and 110 km. Analysis products have biases in the stratosphere and above due to the decreasing amount of operational observations available for data assimilation systems. We investigate differences between two state-of-the-art analysis products, namely that of the Integrated Forecasting System, IFS, from the European Center for Medium-range Weather Forecast and that of the ICOsahedral Nonhydrostatic model, ICON, from the German Weather Service. We compare their differing predictions of acoustic waveguides across the International Monitoring System (IMS) of the CTBT. We demonstrate significant differences in prediction of waveguide strength in the equatorial region, related to different amplitudes of the westerly phase of the Semi-Annual Oscillation. Waveguide occurrence predictions can differ by up to 40% across the IMS, in the meridional and zonal directions. We quantify biases with respect to LiDAR wind and temperature observations at three sites. We demonstrate biases of up to 40% and 60% in terms of waveguide occurrence prediction for ICON and IFS, respectively, using the Institute for Atmospheric Physics's LiDAR simultaneous wind and temperature observations. We stress the added-value for more high-resolution measurements in the tropical region where operational products strongly disagree at altitudes that matter for infrasound propagation.Plain Language Summary Weather forecast products are issued daily and feed different operational activities relying on knowledge of the atmospheric state. Among those, the monitoring of the atmosphere with infrasound technology has been put in place to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). To localize and characterize acoustic sources of interest, meteorological conditions from the surface to high altitudes (120 km) are needed. Indeed winds and temperatures up to ∼120 km height can affect the way acoustic waves propagate through atmospheric layers across large distances (up to 1,000 s of km) before being detected at infrasound stations of the International Monitoring System (IMS). Two state-of-the-art meteorological products are compared with respect to their prediction of acoustic waveguides. They are respectively issued by the European Center for Medium-range Weather Forecast (ECMWF) and by the German Weather Service (DWD). We find notable difference across the IMS and more specifically in equatorial regions in the upper stratosphere where the Semi-Annual Oscillation's amplitude differs between products. We also compare the products with ground-based LiDAR observations, allow scanning of the vertical atmospheric structure at three sites to identify notable differences. This further supports the importance of using measurements to help improve and validate these high-resolution models
A parsimonious tail compliant multiscale statistical model for aggregated rainfall
No full textInternational audienceModeling rainfall intensity distributions across aggregation scales (from sub-hourly to weekly) is essential for hydrological risk analysis and IDF curves. Aggregation naturally imposes mathematical constraints: return levels must be ordered by time scale, as daily accumulations necessarily exceed sub-daily ones. From a statistical perspective, each aggregation step should ideally not require additional parameters, yet parsimonious models describing the full distribution remain scarce, as most literature focuses on seasonal block maxima. In this study, we propose a parsimonious framework to model all rainfall intensities (low to large) across scales. We utilize the Extended Generalized Pareto Distribution (EGPD), which aligns with extreme value theory for both tails while remaining flexible for the bulk of the distribution. We establish a general result on the behavior of EGPD variables under various aggregation procedures. To overcome the difficulty of direct likelihood inference, we link the EGPD class to Poisson compound sums. This allows the use of the Panjer algorithm for efficient composite likelihood evaluation. Our approach ensures that return levels do not cross across scales and enables estimation for return periods below annual or seasonal levels. We demonstrate the method using sub-hourly series from six French stations with diverse climates. Only eight parameters are needed per station to capture scales from six minutes to three days. IDF curves above and below the annual scale are provided
Holocene climatic changes in the Kerguelen archipelago (South Indian Ocean) based on marine and lacustrine palaeoclimatic archives
No full textInternational audienceClimatic variability in the Southern Hemisphere is largely controlled by the latitudinal position of the Southern Hemisphere Westerly Winds (SHW), whose migration influences precipitation, temperature, and Antarctic upwelling. This study presents the results of analyses of two lacustrine sediment cores from Lake Armor, located on the subantarctic Kerguelen Islands (49 • 15′S, 69 • 10′E), within the SHW belt. Lipid biomarkers (Glycerol Dialkyl Glycerol Tetraethers, n-alkanes, and their hydrogen isotopes) were used to reconstruct mean annual air temperature above freezing (MAF) and humidity conditions. These records are compared with a high-resolution diatom-based summer sea surface temperature (SST) reconstruction from marine core MD11-3353, situated 150 km southwest of Lake Armor. In the late glacial and Early Holocene, our results reveal a period of warm air temperature, comparable to current values and very warm sea surface temperature, 5°C above the current values. Around 9000 cal a BP, an abrupt transition occurred, marked by a cooling of 5°C in SST and 1.5°C in MAF, interpreted as a northward migration of the SHW and associated oceanic fronts. The Mid-to-Late Holocene period is characterized by pronounced MAF variability, including a notably warm interval between 3000 and 2000 cal a BP, when n-alkane dD suggests the prevalence of wetter conditions. Since ~250 cal a BP, a southward migration of the SHW has produced a 2.5°C rise in MAF. Our findings are overall consistent with previous studies from the Indian Ocean, but permit us to go a step further as by comparing SSTs and air temperatures. This suggests that SST is not a reliable predictor of air temperature on the Kerguelen Islands, particularly during the Early Holocene. We hence argue that Kerguelen air temperature is predominantly controlled by the position of westerly winds, as an indicator of reorganisations in air mass trajectories
Tara Polaris expeditions: Sustained decadal observations of the coupled Arctic system in rapid transition
No full textThe coupled Arctic system is in rapid transition and is set to undergo further dramatic changes over the coming decades. These changes will lead most likely to an ice-free ocean in summer, expected before mid-century. The Arctic will become more strongly influenced by atmospheric and oceanographic processes characteristic of mid-latitudes, increasing the prevalence of contaminants and new biological species. This ongoing transition of the Arctic to a new state necessitates systematic monitoring of all sentinels (variables that make an essential contribution to characterizing the Earth's state) to improve our understanding of the system, enhance forecasting and support knowledge-based decisions. Here, we describe a sustained multi-decadal observation program to be implemented on the Tara Polar Station between 2026 and 2046. The monitoring program is designed as a series of year-long drift expeditions, called Tara Polaris, in the central Arctic Ocean, covering all seasons. The multidisciplinary data will bridge ecological, geochemical, biological, and physical parameters and processes in the atmosphere, sea ice and ocean. In addition, data collected with consistent methodologies over a 20-year period will make it possible to distinguish long-term trends from seasonal and interannual variability. In this paper, we discuss specific measurement challenges in each compartment (i.e., atmosphere, sea ice and ocean) along key sentinels and the most pressing scientific questions to be addressed. The expected outcomes of the Tara Polaris program will enable us to understand and quantify the main feedbacks of the coupled Arctic system, with their seasonal and interannual trends and spatial variability.</div
Christian Grataloup Vincent Lemire, 2025, Atlas historique du Moyen-Orient, Paris, L’histoire - Éditions les Arènes, 189 p.
No full textInternational audienceCompte-rendu de l'atlas historique du Moyen-Orient de Christian Grataloup et Vincent Lemire, mis en perspective avec l'atlas éponyme paru en 2020 par Florian Louis
Systematic home visit planning prior to hospital discharge: a propensity-score matched comparative cohort study of over one million mother-infant dyads with one-year follow-up
No full textInternational audienceProblemMaternal mental health problems are leading causes of morbidity and mortality in high-income countries, yet follow-up after birth remains inconsistent.BackgroundSystematic postnatal home visits are recommended but many women do not receive them. clinical and economic impact of a structured scheduling of visits before discharge has not been fully evaluated.AimTo determine whether systematically arranged postpartum home visits were associated with reduced maternal rehospitalisations for mental health conditions. Secondary objectives included maternal and infant outcomes and healthcare costs within the first year.MethodsWe conducted a matched cohort study using national administrative data from 1297,646 low risk mother-infant dyads. In the intervention group, a midwife home visit was scheduled before discharge. Controls were matched on demographic and obstetric variables. The main outcome was maternal rehospitalisation for mental health conditions (ICD-10 codes F30–F45, F48, including depression or anxiety) within one year postpartum, excluding psychoses (F20–F29). Secondary outcomes included all-cause rehospitalisation for mothers and/or infants, use of emergency services, mortality, and overall healthcare costs.FindingsA scheduled home visit occurred in 95 % of cases in the intervention group, compared to 52 % in controls (p < 0.0001). The intervention was associated with fewer maternal mental health-related rehospitalisations (RR=0.82, p < 0.0001) and slightly reduced overall rehospitalisation rates for mothers and infants. Mortality was unchanged. Mean healthcare costs were marginally lower in the intervention group.DiscussionSystematic discharge planning may improve continuity of care and reduce psychiatric morbidity.ConclusionsPostpartum home visit scheduling supports better outcomes and may offer modest economic benefits
Rigorous numerical computation of the Stokes multipliers for linear differential equations with single level one
No full textWe describe a practical algorithm for computing the Stokes multipliers of a linear differential equation with polynomial coefficients at an irregular singular point of single level one. The algorithm follows a classical approach based on Borel summation and numerical ODE solving, but avoids a large amount of redundant work compared to a direct implementation. It applies to differential equations of arbitrary order, with no genericity assumption, and is suited to high-precision computations. In addition, we present an open-source implementation of this algorithm in the SageMath computer algebra system and illustrate its use with several examples. Our implementation supports arbitrary-precision computations and automatically provides rigorous error bounds. The article assumes minimal prior knowledge of the asymptotic theory of meromorphic differential equations and provides an elementary introduction to the linear Stokes phenomenon that may be of independent interest
Nanosatellites, CubeSats de l’ère NewSpace pour l’observation spatiale 2: Conception et mise en oeuvre de CubeSats
No full textInternational audienceNanosatellites, CubeSats of the NewSpace Era for Space Observation 2 presents the entire life cycle of a CubeSat, from the design phase to orbital operations.The CubeSat nanosatellite carries instruments designed for space observation and study, integrated into a mechanical architecture that supports the control and communication electronics. This mechatronic system is optimized to ensure maximum robustness and reliability under operational conditions. Internal couplings within the satellite’s architecture, as well as external interactions with the space environment – whether thermal, vibrational, electromechanical, thermomechanical, electro-thermomechanical, or related to electromagnetic compatibility – are modeled using the finite element method. Environmental testing such as HALT/HASS, based on experience from previous missions and simulation results, allows for the integration of a reliability-based design optimization (RBDO) approach.This book also traces the evolution of our knowledge and methods regarding light, an essential payload component and luminous phenomena from Antiquity to the end of the Middle Ages, and discusses current advances in quantum optics, including wave-particle duality, quantum entanglement of photons, and vacuum fluctuations, sources of technological innovations.Le nanosatellite CubeSat embarque des instruments destinés à l’observation et à l’étude de l’espace, intégrés dans une architecture mécanique supportant l’électronique de commande et de communication. Nanosatellites, CubeSats de l’ère NewSpace pour l’observation spatiale 2 présente l’ensemble du cycle de vie d’un CubeSat, depuis la phase de conception jusqu’à celle de l’exploitation en orbite. Ce système mécatronique est optimisé afin de garantir une robustesse et une fiabilité maximales en conditions opérationnelles.Les couplages internes à l’architecture du satellite, ainsi que les interactions externes avec l’environnement spatial — qu’il s’agisse de phénomènes thermiques, vibratoires, électromécaniques, thermomécaniques, électrothermo-mécaniques ou liés à la compatibilité électromagnétique — sont modélisés à l’aide de la méthode des éléments finis. Les essais environnementaux de type HALT/HASS, fondés sur l’expérience de missions antérieures et les résultats de simulation, permettent d’intégrer une démarche de conception fiabiliste RBDO.Enfin, l’ouvrage retrace l’évolution de nos connaissances et de nos méthodes sur le phénomène lumineux et la lumière depuis l’Antiquité jusqu’à la fin du Moyen Âge et aborde les avancées actuelles de l’optique quantique, sur la dualité onde-corpuscule, l’intrication quantique des photons et les fluctuations du vide
Econometrics at the Extreme: From Quantile Regression to QFAVAR <sup>1</sup>
No full textInternational audienceABSTRACT This paper surveys quantile modelling from its theoretical origins to current advances. We organize the literature and present core econometric formulations and estimation methods for: (i) cross‐sectional quantile regression; (ii) quantile time series models and their time series properties; (iii) quantile vector autoregressions for multivariate data; (iv) quantile panel models for longitudinal data; and (v) quantile factor‐augmented models for information compression in data‐rich environments. Each section outlines theoretical foundations and developments, followed by representative empirical applications. Finally, the survey highlights open gaps in quantile modelling. By studying distributional dynamics beyond averages, quantile methods provide policymakers and regulators with tools to design interventions that are robust to risks and effective across the entire spectrum of possible outcomes
HIV persistence in tissues on dolutegravir-based therapy is not associated with resistance mutations to dolutegravir
No full textInternational audienceDespite ongoing transcriptional activity, persistence of HIV-1 in deep tissues is not associated with the selection of DRMs to dolutegravir on intact proviruses. Our results suggest that the detectable transcriptional activity stems predominantly from defective proviral DNA