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Land surface model underperformance tied to specific meteorological conditions
No full textInternational audienceThe exchange of carbon, water, and energy fluxes between the land and the atmosphere plays a vital role in shaping global change and extreme events. Yet our understanding of the theory of this surface-atmosphere exchange, represented via land surface models (LSMs), continues to be limited, highlighted by marked biases in model-data benchmarking exercises. Here, we leveraged the PLUMBER2 dataset of observations and model simulations of terrestrial sensible heat, latent heat, and net ecosystem exchange fluxes from 153 international eddy-covariance sites to identify the meteorological conditions under which land surface models are performing worse than independent benchmark expectations. By defining performance relative to three sophisti-cated out-of-sample empirical models, we generated a lower bound of performance in turbulent flux prediction that can be achieved with the input information available to the land surface models during testing at flux tower sites. We found that land surface model performance relative to empirical models is worse at edge conditions -that is, LSMs underperform in timesteps where the meteorological conditions consist of coinciding relative extreme values. Conversely, LSMs perform much better under "typical" conditions within the centre of the meteorological variable distributions. Constraining analysis to exclude the edge conditions results in the LSMs outperforming strong empirical benchmarks. Encouragingly, we show that refinement of the performance of land surface</div
Non-aqueous leaching of critical metals from black mass of spent lithium-ion batteries using a reusable acidic organophosphorus extractant
No full textInternational audienceRecycling critical metals from the black mass of spent lithium-ion batteries (LIBs) is essential for supply security and waste management. Conventional hydrometallurgical acid leaching is effective but generates large volumes of wastewater. In this study, a non-aqueous leaching system has been developed using an acidic organophosphorus extractant, di-(2-ethylhexyl)phosphoric acid (D2EHPA), as the lixiviant, consolidating leaching and solvent extraction (SX) into a single stage. Metallic copper and aluminum were evaluated as reductants; only copper enabled effective leaching in D2EHPA. Key parameters (stirring speed, copper dosage, D2EHPA concentration, temperature, time, and pulp density) were optimized. The optimum was 700 rpm, 0.15 g Cu per g black mass, 2.0 M D2EHPA, 90 • C, 4 h, and 1.0 g black mass per 20 mL D2EHPA. Under these conditions, leaching efficiencies were ~100 % for Li, 79.2 % for Ni, 94.6 % for Co, 47.3 % for Mn, and 96.4 % for Cu (reductant). D2EHPA was reusable over five leaching-stripping cycles with negligible performance loss. Metals were recovered from the loaded organic by (i) pH-controlled aqueous stripping and (ii) oxalic-acid precipitation stripping. The study also examined the potential of using copper-containing waste, such as waste printed circuit boards (WPCBs) and Cu-Al foil from spent LIBs as reducing agents, enabling an integrated waste-recycling scheme. This non-aqueous leaching process reduces unit operations and lowers chemical and water consumption while maintaining high recovery for key metals.</div
Numerical simulations of oscillating and differentially rotating neutron stars
No full textThe remnants of binary neutron star mergers are expected to be massive, rapidly rotating stars whose oscillations produce gravitational waves in the kilohertz band. The degree of differential rotation and the rotation profiles strongly influence their structure, stability and oscillation spectrum, and must therefore be taken into account when modeling their dynamics. We extend the pseudospectral code ROXAS (Relativistic Oscillations of non-aXisymmetric neutron stArS) to enable the dynamical evolution of oscillating, differentially rotating neutron stars. Using the updated code, we aim to study the star's oscillation frequencies. We extend the previous formalism, based on primitive variables and the conformal flatness approximation, to differential rotation. Within this framework, we run a series of axisymmetric and non-axisymmetric simulations of perturbed, differentially rotating neutron stars with different rotation rates, and extract their oscillation frequencies. Axisymmetric modes, as well as those under the Cowling approximation, show excellent agreement with published results. We show that the secondary fundamental mode in the Cowling approximation is an artifact that does not appear in dynamical spacetimes. In addition, we provide, for the first time, frequency values for non-axisymmetric modes in differentially rotating configurations evolved in conformal flatness. This extension broadens the range of physical scenarios that can be studied with ROXAS, and represents a step toward more realistic modeling of post-merger remnants and their gravitational-wave emission
Multiple comparisons of point clouds acquired by a permanent LiDAR (PLS) to improve the reliability of a rockfall event catalogue
No full textInternational audienceThe ANR C2R-IA project (www.anrc2ria.fr) aims to develop reliable decision-support tools for the dynamic management of rockfall hazard. Its goal is to understand how meteorological forcing influences rockfall occurrence and to anticipate temporary increases in hazard in order to implement risk reduction measures. To this end, a predictive model of rockfall occurrence as a function of meteorological conditions is being developed using artificial intelligence tools (neural network training), which requires a comprehensive and well-labelled dataset. Several monitoring instruments have been deployed at the Saint-Eynard site (Grenoble, France). Among them, a permanent LiDAR scanner (PLS) acquires point clouds continuously, with one acquisition per hour, providing high temporal resolution representative of what could be used for operational monitoring or crisis management. An automated data-processing workflow has been developed in Python. It is based on a pairwise comparison of the clouds (Manceau et al., 2025) and includes the alignment of successive point clouds, filtering of points outside the cliff area, change detection using M3C2 distances computation, clustering with DBSCAN, and volume quantification of rockfalls using alphashapes. This well-structured processing has significantly reduced the detection threshold, identifying relief change of only 10 cm deep (compared to 40 cm previously; Le Roy et al, 2020) and 10 liters in volume, while the scanner is located approximately 1 km from the cliff. Depending on acquisition quality, the effective temporal resolution of detected rockfall events may range from one hour to several days. Combining relief-change detections with simultaneously deployed seismic monitoring should further refine event timing. The completeness of the event catalogue has therefore improved, increasing from fewer than 10 detected rockfalls per month to around 30. However, some false positives remain, mainly related to recurring artifacts despite preprocessing. To mitigate these errors, the previous pairwise comparison of the clouds has been refined to a multiple point-cloud comparison strategy, enabling the tracking of the temporal persistence of changes. This allows distinguishing changes corresponding to real rockfalls, which persist over time, from transient artifacts. This improvement leads to a more reliable and complete rockfall event database. It includes block shape ratios, identified failure mechanisms, and free-fall heights under overhanging sections, providing a suitable basis for future fusion with seismic data.Manceau, L., Chanut, M.-A., Levy, C., Dewez, T., and Amitrano, D.: Enhancing Rockfall Detection Using Permanent LiDAR Scanner (PLS) Data and Automated Workflows at St. Eynard Cliff (Grenoble, France), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6312, https://doi.org/10.5194/egusphere-egu25-6312 Le Roy, G., Helmstetter, A., Amitrano, D., Guyoton, F., & Le Roux-Mallouf, R. (2019). Seismic analysis of the detachment and impact phases of a rockfall and application for estimating rockfall volume and free-fall height. Journal of Geophysical Research: Earth Surface, 124, 2602-2622. https://doi.org/10.1029/2019JF00499
Compounded effects of long-term warming and the exceptional 2023 marine heatwave on North Atlantic coccolithophore bloom dynamics
No full textInternational audienceThe North Atlantic is undergoing rapid ecological evolution under the influence of both long-term warming and the increasing frequency of marine heatwaves. In 2023, the North Atlantic experienced record-breaking sea surface temperature anomalies, exceeding +5 °C regionally and lasting several months. Using 25 years of satellite-derived particulate inorganic carbon data (1998–2023), we assess the response of coccolithophore blooms across two biogeographical boundaries: the Celtic Sea and the Barents Sea. We show that the 2023 marine heatwave led to reduced bloom intensity and fragmentation in the Celtic Sea, while leading to record-high intensity and extent in the Barents Sea. These contrasting responses are modulated by long-term sea surface temperature trends, upper-ocean stratification, and polar front shifts. Our findings suggest a spatial shift of coccolithophore blooms with potential implications for the carbon cycle under long-term warming and stratification
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
Kinematic lensing with high-resolution spectroscopic surveys. A unique opportunity for transformative cosmology at high redshifts in the 2040s
No full textInternational audienceWe present a science case to perform high-redshift cosmic shear surveys for cosmology with next-generation spectroscopic instruments, such as the proposed MegaMapper and Wide-field Spectroscopic Telescope. We argue that by using the novel technique called 'kinematic lensing' (KL) it will be possible to obtain shear catalogues at redshifts between 2 and 5. We show that the signal-to-noise ratio of KL at such high redshifts is on average twice as much that expected from current weak lensing (WL) surveys such as Euclid or LSST, and several times that of the previous generation of WL surveys like DES and KiDS, even with very conservative assumptions about the fraction of spectroscopically-detected sources for which KL shear estimates will be available. This will allow cosmologists to perform joint galaxy clustering-cosmic shear analyses over unprecedented cosmic volumes and to probe the growth of structures deep in the matter-dominated era and across the onset of dark-energy domination, offering a unique opportunity to unveil the mystery of cosmic acceleration
On the tropical nature of an intense Mediterranean cyclone in the ocean-atmosphere system
No full textInternational audienceThe Mediterranean basin hosts a large number of cyclones every year. Among them, some rare cases named medicanes present similarities with tropical cyclones but their dynamical characteristics are debated. The ocean-atmosphere dynamics of Medicane Ianos (2020) are studied here through km-scale fully coupled ocean-wave-atmosphere simulations. These allow investigating the tropical nature of Ianos in terms of both atmospheric circulation and thermal structure, and of oceanic cold wake response which feedbacks negatively onto the cyclone's intensity. Simulations match in situ and remotely sensed observations in the ocean and atmosphere well. Three life cycle phases can be distinguished with a mature phase during which the cyclone is compact and axisymmetric. Orographic acceleration is shown to induce asymmetry in the cyclonic winds and precipitation prior to landfall. These are expected to be common for medicanes given the small scale and steep orography of the Mediterranean basin. Ianos distinguishes itself from previous medicanes by its intense cold wake wherein the sea surface cooling exceeds 3\textdegree{C}. The wake results mainly from mixing at the base of the mixed layer, while surface fluxes play a secondary role as revealed by temperature budget analysis. The amplitude and dynamics of the wake are alike those found in tropical cyclones of category 2 or more. A deep warm core cyclonic eddy on Ianos' track is responsible for an interruption in the cold wake which coincides with the re-intensification of the cyclone during its mature phase. Such eddies are widespread in the Mediterranean but poorly constrained in models
Intra-night optical polarization monitoring of blazars
No full textInternational audienceBlazars are known for their extreme variability across the electromagnetic spectrum. Variability at very short timescales can push the boundaries between competing models offering us much needed discriminating power. This is particularly true for polarization variability that allows us to probe particle acceleration and high-energy emission models in blazars. Here we present results from the first pilot study of intra-night optical polarization monitoring conducted using RoboPol at the Skinakas Observatory and supplemented by observations from the Calar Alto, Perkins, and Sierra Nevada observatories. Our results show that while variability patterns can widely vary between sources, variability on timescales as short as minutes is prevalent in blazar jets. The amplitude of variations are typically small, a few percent for the polarization degree and less than 20 degrees for the polarization angle, pointing to a significant contribution to the optical emission from a turbulent magnetic field component, while the overall stability of the polarization angle over time points to a preferred magnetic field orientation
Type Ia supernova feedback effects on globular clusters of different masses
No full textInternational audienceThrough 3D hydrodynamical simulations, we explore the impact of Type Ia supernova (SN) explosions on the star formation history and chemical properties of second-generation (SG) stars in young globular clusters with masses of 10^5-10^6 Msun. We assume that the SG is formed out of the asymptotic giant branch (AGB) ejecta of first-generation stars plus pristine interstellar medium gas which is modelled as a uniform gas moving at a constant velocity towards the cluster. We tested two values for the infalling gas density of 10^(-24) and 10^(23) g/cm^3. Type Ia SNe start to explode together with the release of gas from the most massive AGB stars. Three simulated models are analyzed. In the low-mass and low-density scenario, we find that SNe Ia quench star formation which however restarts when the gas cools down again in between two explosions. SG stars are dominated by a He-rich population (Y>0.33), which is poorly diluted by pristine gas. In the high-mass models, star formation is mildly affected, while the He composition is significantly altered as exploding SNe prevent the accretion of pristine gas and therefore extremely helium-rich stars form. In the high-density model, such weak gas accretion leads to a maximum enhancement in helium mass fraction much larger than the observed one and not correlating with the initial cluster mass as found in models without Type Ia SNe. As for the iron content, small spreads have been found in all models, but the SG is less homogeneous than the FG, at variance with current observations