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Predictability of North Pacific blocking events: Analogue‐based analysis of historical MIROC6 simulations
No full textInternational audienceAtmospheric blocking exerts a profound influence on midlatitude circulation, yet its predictability remains elusive, due to intrinsic nonlinearities and sensitivity to initial conditions. While blocking dynamics have been extensively studied, the impact of geographical positioning on predictability remains largely unexplored. This study provides a comparative assessment of the predictability of western and eastern North Pacific blocking events, leveraging analogue‐based diagnostics applied to Coupled Model Intercomparison Project Phase 6 (CMIP6) Model for Interdisciplinary Research on Climate, version 6 (MIROC6) simulations. Blocking structures are identified using geopotential height gradient reversal, with their temporal evolution analyzed through trajectory tracking and error growth metrics. Results reveal that eastern blocks exhibit lower predictability, characterized by rapid error divergence and increased mean logarithmic growth rates compared with western blocks. Persistence analysis gives no significant difference between eastern and western North Pacific blocking events. Sensitivity analyses across varying detection thresholds validate the robustness of these findings
A Framework for Minimizing the Impact of Wet Antenna Attenuation on Rainfall Estimates Provided by Commercial Microwave Links
No full textInternational audienceThe compensation of the extra attenuation introduced by wet antennas is crucial to get reliable rainfall intensity estimates from the data collected by commercial microwave links (CMLs). This study reviews the available wet antenna attenuation (WAA) models and proposes a new framework for calibrating WAA model parameters, based on rain gauge measurements (assumed as ground truth). The framework has been applied to the data measured by 86 CMLs located in the Seveso River basin (Northern Italy) during 44 rainy days in 2019-2020. As most WAA models are basically equivalent in spite of different formulations, we selected only a subset, including the Schleiss-Rieckerman-Berne model (SRB) and the Valtr-Fencl-Bareš (VFB) model, the latter in the versions with the original parameter values and with the parameters calibrated over our CML data (VFBm). We found that WAA increases with rainfall intensity, as predicted by the VFB model, and it is weakly dependent on link frequency. We derived two sets of optimum WAA model parameters for the Ka-band (17-23 GHz) and the Q-band (37-43 GHz), respectively. WAA values are up to 4 dB at heavy rainfall intensities (50 mm/h) in the Q-band. The VFBm model performs better than VFB and outperforms SRB, when assessed over the entire set of CML data and over different classes of CMLs (based on distance to the neighbor rain gauge, frequency, and path length) or, again, over different classes of rainfall intensity.</div
Panorama rapide de l’actualité « Numérique » de la semaine 8 janvier au 15 janvier 2026
No full textInternational audienceAnalyse de l'actualité du droit du numérique (janvier 2026) I.Données 1)Données publiques (environnementales) (demandes anonymes) : CJUE du 15 janvier 2026 Arrêt de la Cour dans l’affaire C-129/24 | Coillte Cuideachta Ghníomhaíochta Ainmnithe2)Données personnelles de 24 millions d’abonnés compromises : 42 M€ d’amendes CNIL contre Free et Free Mobile : Délibération SAN-2026-001 du 8 janvier 2026 - Légifrance - Délibération SAN-2026-002 du 8 janvier 2026 - Légifrance3)La cour des comptes s’intéresse au déploiement de l’intelligence artificielle au sein de France Travail : un rapport publié le 7 janvier 2026II.Plateformes1)Le Recours de Google contre la sanction en antitrust de la Commission : Recours introduit le 20 novembre 2025 – Google et Alphabet/Commission (Affaire T-794/25) : (C/2026/185)2)Zalando contre Commission européenne (qualification de « très grande plateforme » - DSA) : Pourvoi formé par Zalando SE contre l’arrêt rendu par le Tribunal (septième chambre élargie) le 3 septembre 2025 dans l’affaire T-348/23, Zalando contre Commission européenne, introduit le 13 novembre 2025 : ELI: http://data.europa.eu/eli/C/2026/161/oj Affaire C-724/25.III.Écologie numériqueLa hausse de la consommation électrique des centres de données : rapport de l’Agence de la transition écologique (Ademe) : un rapport publié le 6 janvierIV.Régulation du réseau1)Rome II et jeux d’argent en ligne : CJUE, 15 janvier 2026, affaire C-77/24 | [Wunner]2)Le retrait des États-Unis des organisations internationales du numérique : mémorandum publié le 7 janvier et communiqué de la Maison-Blanche
Tara Polaris expeditions: seasonal and long-term contaminant monitoring in the changing central Arctic
No full textInternational audienceThe central Arctic atmosphere, cryosphere, hydrosphere and biosphere, is heavily impacted by anthropogenic activities. While some contaminants originate from local activities, the majority are transported over long distances via rivers, ocean currents, and atmospheric pathways. Contaminants can have adverse effects on the environment, ecosystems, and human health, which are expected to intensify with continued emissions and warming climate. This article outlines the objectives for new studies on contaminants in the Arctic Ocean, in particular during the Tara Polaris expedition, with an emphasis on year-round long-term contaminant dynamics and associated ecotoxicological risks. Mercury contamination remains a major concern in the Arctic, especially in the form of methylmercury, which is primarily produced by marine microbes. Methylmercury bioconcentrates, bioaccumulates and biomagnifies to harmful levels in Arctic wildlife and threatens indigenous communities. Anthropogenic lead (Pb), though low in Arctic waters, remains toxic and may be remobilized by climate change. Plastic pollution, from nano-to macro-scales, is widespread across all Arctic compartments, closely interacting with planktonic communities and posing ingestion risks to invertebrates, fish, seabirds and mammals (including humans). Chemicals of Emerging Arctic Concern (CEAC), including newly recognized persistent organic pollutants inherited from past industrial activities (e.g., per-and polyfluoroalkyl substances (PFAS)), are more recalcitrant in the environment than many other synthetic compounds, raising serious questions about their long-term ecological and health effects. In this context, the Tara Polaris expeditions aim to produce high-resolution, year-round observational data in the central Arctic to deepen our understanding of contaminant sources, transport, internal cycling and environmental fate. These data will also support the development and refinement of numerical models for contaminant dynamics in the context of both Arctic and global environmental change
An Effective Version of the p-Curvature Conjecture for Order One Differential Equations
No full textWe develop an effective version of Kronecker's Theorem on the splitting of polynomials, based on asymptotic arguments proposed by the Chudnovsky brothers, coming from Hermite-Padé approximation. In conjunction with Honda's proof of the p-curvature conjecture for order one equations with polynomial coefficients we use this to deduce an effective version of the Grothendieck p-curvature conjecture for order one equations. More precisely, we bound the number of primes for which the p-curvature of a given differential equation has to vanish in terms of the height and the degree of the coefficients, in order to conclude it has a non-zero algebraic solution. Using this approach, we describe an algorithm that decides algebraicity of solutions of differential equation of order one using p-curvatures, and report on an implementation in SageMath.</div
Demonstrating Aeolus capability to observe wind-cloud interactions
No full textInternational audienceModel based studies have shown interactions between wind vertical profiles and cloudiness, but few observational studies corroborate them. The unique observations of Aeolus spaceborne Doppler wind lidar can contribute to fill this gap. In this paper, we merged global Aeolus observations of cloud profiles at full horizontal resolution (3 km along orbit track) with co-located profiles of horizontal winds.We first observed wind-cloud interactions at regional scale over the Indian Ocean. Aeolus captures the strengthening of the Tropical Easterly Jet in early June 2020, with wind speeds exceeding 40 m s -1 in its core, and a simultaneous increase of high cloud fraction up to above 30 %, until the decay of the jet during fall.Secondly, we observed wind-cloud interactions at cloud scale (between 3-100 km) in different regions. Over the Indian Ocean as well as over cumulus and stratocumulus dominated regions, we found that the wind shear inside clouds is smaller than the wind shear in the clear sky surrounding the clouds (statistically significant). In addition, we found that the wind speed difference between the cloud and its surrounding clear sky increases with the clear sky wind shear, especially in cumulus (R = -0.94) and stratocumulus (R = -0.87) dominated regions. This study demonstrated that despite its coarse resolution, Aeolus can capture wind perturbations induced by convective motion.</div
Rapport sur les services climatiques réussis dans le monde et leurs critères de succès: Livrable commun au Projet ciblé TRACCS-PC1-DIALOG (D5.3) et au Projet Ciblé TRACCS-PC3-DEMOCLIMA (D1)
No full textLes enjeux socio-économiques liés aux effets du réchauffement climatique sont tels qu’une demande croissante d’informations climatiques adaptées pour la mise en place de stratégies d’atténuation et/ou d’adaptation est clairement exprimée par les secteurs économiques (e.g. agriculture, énergie, tourisme, infrastructures terrestres ou maritimes, etc…) et par les territoires/régions qui mesurent pleinement leursvulnérabilités. En réponse à ces demandes, de nombreux projets de recherche nationaux (e.g., la "Convention relative à l’attribution d’un appui financier au bénéfice des services climatiques", signée entre le Ministère de la Transition Écologique et Solidaire (MTES) et le CNRS en mars 2017, ou le développement du portail DRIAS), européens (e.g., le programme ERA4CS « European Research Area for Climate Services » du JPI Climate, ou encore Copernicus) ou internationaux (e.g., les outils développés par la NASA, le GIEC…) ont permis le financement de « services climatiques ». Plusieurs acteurs opérationnels nationaux et européens développent et mettent à disposition des « services climatiques » via des plateformes souvent libres d’accès et enfin, apparaissent sur le marché des bureaux d’études dont l’activité commerciale vise le développement de « services climatiques » à la carte et adaptés aux demandes des clients.L’offre pour les « services climatiques » est donc aujourd’hui multiforme par l’information fournie (données climatiques « simples », indicateurs, outils d’aide à la décision) et par son mode de développement. Face à cette diversité, les enjeux sont de documenter et comprendre le paysage des services climatiques actuels, de faire ressortir les besoins, et de se munir de moyens pour caractériser la réussite des services climatiques, pour évaluer l'existant et guider le développement de nouveaux projets. Menée conjointement par les projets ciblés DIALOG (PC1) et DEMOCLIMA (PC3) du PEPR TRACCS, cette étude vise quatre objectifs :i) Documenter le paysage actuel des services climatiques (section 2) en France et dans le monde (identifiés par la communauté TRACCS) en les présentant par usages et cibles ;ii) Identifier des besoins non satisfaits vis-à-vis des services climatiques (section 4) ;iii) Identifier un ensemble de critères de réussite d'un service climatique pour les évaluer (section 5) ;iv) Proposer des bonnes pratiques pour atteindre ces critères de réussite (section 6); ces éléments guideront les choix des futurs démonstrateurs qui seront conçus et développés au sein de DEMOCLIMA.Notre travail repose en grande partie sur le recueil de dires d'acteurs des "services climatiques", dans une approche "bottom-up"
Sur les équations de Navier-Stokes issues de la rotation d’un obstacle dans un fluide
No full textWe consider the modified Navier-Stokes equations in R3 describing the motion of a fluid in the presence of a rotating rigid body. Weighted Sobolev spaces are used to describe the behavior of solutions at large distances. Under suitable assumptions, w e prove the existence and regularity of solutions satisfying appropriate conditions at infinity.Nous considérons les équations de Navier-Stokes modifiées dans R3 décrivant le mouvement d’un fluide en présence d’un corps rigide en rotation. Des espaces de Sobolev à poids sont utilisés pour décrire le comportement des solutions à grande distance. Sous des hypothèses appropriées, nous prouvons l’existence et la régularité de solutions satisfaisant des conditions adéquates à l’infini
Association Between Metabolic Syndrome, Obesity, and Cognitive Performances in Individuals With Bipolar Disorders: Cross‐Sectional and Longitudinal Analyses in the FACE ‐ BD Cohort
No full textInternational audienceIntroduction: Metabolic syndrome (MetS) has been suggested to be associated with cognitive impairments in bipolar disorder (BD); however, studies are limited by small sample sizes or cross-sectional design. Our objective is to evaluate the cross-sectional and longitudinal associations between MetS and cognitive performances in a large cohort of individuals with BD.Methods: 1175 individuals with a DSM-IV diagnosis of BD were included from the FACE-BD cohort, assessed with a standardized battery of clinical and neuropsychological tests and followed up with a cognitive retest at 2 years for a subsample (n = 367). A global cognitive index was created by using a Principal Component Analysis. Associations between MetS and cognitive performances at baseline were explored using multiple analyses of covariance and linear mixed models were used for longitudinal data.Results: The prevalence of MetS was 21.5% in this sample. Multivariable analyses identified associations between MetS and poorer cognitive performance in the cross-sectional analysis, independently of age, gender, education level, psychotropic treatments, and comorbidities. Specifically, individuals with MetS showed poorer results (global cognitive index, cognitive flexibility, inhibition, and verbal memory). After adjustment, the longitudinal analysis showed no change in the global cognitive index at year 2 and no time × metabolic syndrome interaction.Conclusions: Our results suggest that MetS is cross-sectionally, but not longitudinally, associated with poorer cognitive performances in BD. This study highlights the importance of systematically and accurately screening for metabolic abnormalities in individuals with BD, and screening for cognitive deficit especially in individuals with MetS. Our results suggest that MetS is not a risk factor for cognitive decline during the follow-up, but further longitudinal studies are required
