ORCID Profile
0000-0003-4864-0181
Current Organisation
FrontierSI
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Publisher: Copernicus GmbH
Date: 08-05-2013
DOI: 10.5194/NHESSD-1-1823-2013
Abstract: Abstract. Whereas major tsunamis have recently affected the southwest Indian Ocean, tsunami hazard in this basin has never been thoroughly examined. Our study contributes to fill in this lack and focuses on La Réunion island for which tsunami hazard related to great earthquakes is evaluated by modeling the scenarios of major historical events. Then, our numerical modeling allow us to compare the tsunami impact at regional scale according to the seismic sources we thus identify earthquakes locations which most affect the island and describe the impact distribution along its coastline. Thirdly, detailed models are performed for selected sites based on high resolution bathymetric and topographic data they provide estimations of the water currents, wave heights and potential inundations. When available, field measurements and tide records allow testing our models. Arrival time, litude of the first wave and impact on the tide gauge time series are well reproduced. Models are consistent with the observations. The west coast of La Réunion is the most affected (to 2.7 m in the harbour of Le Port Est for 2004 event) by transoceanic tsunamis. Numerical modeling has been performed at Saint-Paul for the 2004 Sumatra-Andaman event and 1833 Sumatra event the low topography of this town could make it vulnerable to tsunami waves. Harbours, particularly prone to undergo significant damages, are also examined. Outside the harbours as well as at Saint-Paul, inundations are predicted along the coastline due to important local wave heights ( 2.5 m).
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-6368
Abstract: & & & & & span& The GRACE Follow-On mission is the first twin-satellite mission& /span& & span& equipped with a laser ranging interferometer (LRI) to measure the inter-satellite distance between the pair of satellites. The LRI operates independently of the K/Ka-band interferometer (KBR& /span& & span& )& and uses& /span& & span& & wavelengths& /span& & span& & & /span& & span& & /span& & sup& & span& & /span& & /sup& & span& & times& /span& & span& & shorter than the K-band& /span& & span& & system.& & & /span& & span& Released at the end of July 2019, the LRI range data is& & /span& & span& therefore& & /span& & span& expected to be of higher accuracy than the KBR and offers the possibility of a better spatial resolution. We compare the LRI and KBR observations of the GRACE-FO mission, from launch to December 2019, to assess the quality of the new LRI system.& /span& & span& & & /span& & span& Spectral analysis of the level1B data shows that the noise level of the LRI is 3& & /span& & span& orders& /span& & span& & of magnitude smaller than the KBR& /span& & span& & and that& & /span& & span& the gravity signal can be detected in the spectral band up to& & /span& & span& mHz in the LRI data& & /span& & span& compared& /span& & span& & to& & /span& & span& mHz& /span& & span& & & /span& & span& i& /span& & span& n& /span& & span& & the& & /span& & span& KBR& /span& & span& & data& /span& & span& .& /span& & span& & & /span& & span& & We compare& /span& & span& & gravity& & /span& & span& fields& /span& & span& & estimated using LRI& & /span& & span& and KBR and show which parts of the spherical harmonic spectrum are affected by the improved accuracy of the LRI observations.& /span& & & & / &
Publisher: American Geophysical Union (AGU)
Date: 2023
DOI: 10.1029/2022JB024330
Abstract: Models of the temporal gravity field derived from space gravity missions are typically produced with monthly temporal resolution and ∼300‐km spatial resolution. However, variations in instrument performance and altitude of the Gravity Recovery and Climate Experiment (GRACE) mission impact the spatial resolution that can be achieved month‐to‐month. As the altitude of the orbits of the twin spacecraft vary throughout the mission, so does the ability of the observations to recover certain components of the temporal gravity field. The spatial resolution of GRACE observations should increase as the altitude decreases throughout the mission because the reduced altitude intensifies the gravity signals acting on the satellites. Simulations using actual GRACE altitude and ground track coverage and realistic noise levels confirm this predicted influence of the altitude of the satellites on the accuracy of the estimated solutions. Solutions with larger mass concentration elements (mascons) are more numerically stable as the satellite altitude decreases but they suffer from greater error caused by the inability to properly represent spatial variations of signals within mascons, referred to as intramascon variability. Mascons as small as ∼150 × 150 km (i.e., ∼1.5 arc‐degree) reduce the intramascon variability and, with appropriate regularization, yield the most accurate solutions, especially during the low‐altitude periods of the GRACE mission. Importantly, unlike spherical harmonic solutions, regularized mascon solutions are not degraded during resonant orbit months, and are of comparable quality to months with full ground track coverage.
Publisher: Springer Science and Business Media LLC
Date: 07-2020
DOI: 10.1007/S00190-020-01395-3
Abstract: The 2004 Sumatra, 2010 Maule, and 2011 Tohoku great earthquakes triggered tsunamis as large as a few decimeters over a few 100 km in the open ocean. The transient ocean mass redistribution propagating as tsunamis changed the Earth’s gravity field enough to perturb the GRACE satellites’ orbits at ~ 500 km above the surface. The on-board microwave ranging system detected inter-satellite acceleration anomalies of up to 1.0–4.0 nm/s 2 . There is good agreement between GRACE measurements and tsunami models for the three events. Complementarily to buoys, ocean bottom pressure sounders, and satellite altimeters, GRACE is sensitive to the long-wavelength spatial scale of tsunamis and provides an independent source of information for assessing alternate early earthquake and tsunami models. Our study demonstrates an innovative way of applying GRACE and GRACE Follow-On data to detect transient geophysical mass changes which cannot be observed by the conventional monthly Level-2 and mascon solutions.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-08-2022
Abstract: Pathogenic variants in genes that cause dilated cardiomyopathy (DCM) and arrhythmogenic cardiomyopathy (ACM) convey high risks for the development of heart failure through unknown mechanisms. Using single-nucleus RNA sequencing, we characterized the transcriptome of 880,000 nuclei from 18 control and 61 failing, nonischemic human hearts with pathogenic variants in DCM and ACM genes or idiopathic disease. We performed genotype-stratified analyses of the ventricular cell lineages and transcriptional states. The resultant DCM and ACM ventricular cell atlas demonstrated distinct right and left ventricular responses, highlighting genotype-associated pathways, intercellular interactions, and differential gene expression at single-cell resolution. Together, these data illuminate both shared and distinct cellular and molecular architectures of human heart failure and suggest candidate therapeutic targets.
Publisher: No publisher found
Publisher: American Geophysical Union (AGU)
Date: 11-04-2014
DOI: 10.1002/2014GL059348
Publisher: Copernicus GmbH
Date: 17-05-2017
Abstract: Abstract. Mass balance changes of the Antarctic ice sheet are of significant interest due to its sensitivity to climatic changes and its contribution to changes in global sea level. While regional climate models successfully estimate mass input due to snowfall, it remains difficult to estimate the amount of mass loss due to ice dynamic processes. It has often been assumed that changes in ice dynamic rates only need to be considered when assessing long-term ice sheet mass balance however, 2 decades of satellite altimetry observations reveal that the Antarctic ice sheet changes unexpectedly and much more dynamically than previously expected. Despite available estimates on ice dynamic rates obtained from radar altimetry, information about ice sheet changes due to changes in the ice dynamics are still limited, especially in East Antarctica. Without understanding ice dynamic rates, it is not possible to properly assess changes in ice sheet mass balance and surface elevation or to develop ice sheet models. In this study we investigate the possibility of estimating ice sheet changes due to ice dynamic rates by removing modelled rates of surface mass balance, firn compaction, and bedrock uplift from satellite altimetry and gravity observations. With similar rates of ice discharge acquired from two different satellite missions we show that it is possible to obtain an approximation of the rate of change due to ice dynamics by combining altimetry and gravity observations. Thus, surface elevation changes due to surface mass balance, firn compaction, and ice dynamic rates can be modelled and correlated with observed elevation changes from satellite altimetry.
Publisher: Springer Science and Business Media LLC
Date: 11-02-2015
Publisher: Copernicus GmbH
Date: 26-09-2022
DOI: 10.5194/GSTM2022-34
Abstract: & & Models of the temporal gravity field derived from space gravity missions are typically produced with monthly temporal resolution and ~300 km spatial resolution. However, variations in instrument performance and altitude of the GRACE mission impact the spatial resolution that can be achieved month-to-month. As the altitude of the orbits of the twin spacecraft vary throughout the mission, so does the ability of the observations to recover certain components of the temporal gravity field. The spatial resolution of GRACE observations should increase as the altitude decreases throughout the mission because the reduced altitude intensifies the gravity signals acting on the satellites. Simulations using actual GRACE altitude and ground track coverage and realistic noise levels confirm this predicted influence of the altitude of the satellites on the accuracy of the estimated solutions. Solutions with larger mass concentration elements (mascons) are more numerically stable as the satellite altitude decreases but they suffer from greater error caused by the inability to properly represent spatial variations of signals within mascons, referred to as intra-mascon variability. Mascons as small as ~150 x 150 km (i.e. ~1.5 arc-degree) reduce the intra-mascon variability and, with appropriate regularisation, yield the most accurate solutions, especially during the low-altitude periods of the GRACE mission. Importantly, unlike spherical harmonic solutions, regularised mascon solutions are not degraded during resonant orbit months, and are of comparable quality to months with full ground track coverage.& &
Publisher: American Association for the Advancement of Science (AAAS)
Date: 03-11-2021
DOI: 10.1126/SCITRANSLMED.ABD3079
Abstract: Stable expression of truncated titin proteins and titin haploinsufficiency characterize TTN cardiomyopathy and represent targets for therapy.
Publisher: American Geophysical Union (AGU)
Date: 02-2022
DOI: 10.1029/2021JB022412
Abstract: The estimation of mass anomalies using Gravity Recovery and Climate Experiment (GRACE) data involves parameterizing the temporal gravity field using basis functions. In this study, we show that the use of irregularly shaped mass concentration (mascon) tiles that follow land/ocean boundaries reduces the leakage of land signals into ocean regions and vice versa. Leakage of signal from continents to oceans in mascons that cross the coastline affect the integrated mass changes at a regional scale. For ex le, the calculated mass loss in 2016 is ∼5% greater for Greenland when using mascons that follow coastlines. We describe efficient algorithms for computing the accelerations acting on the satellites caused by mass changes on mascons, along with the partial derivatives relating the mass changes to the inter‐satellite observations. Through simulation, we quantify the impact of different mascon geometries, spatial resolution and regularization. The variations of mass change signals within mascons, which we call “intra‐mascon variability,” contribute to errors in estimates of mass variation from GRACE data. While this can be mitigated through the regularization of the inversions, it cannot be removed entirely. The use of irregularly shaped mascons that follow land/ocean boundaries reduces the “intra‐mascon leakage” of land signals into ocean regions and vice versa. This approach can also be applied to hydrological basins for calculating integrated mass changes on catchment scales.
Publisher: Oxford University Press (OUP)
Date: 29-04-2013
DOI: 10.1093/GJI/GGT123
Publisher: Elsevier BV
Date: 2022
Publisher: Elsevier BV
Date: 03-2017
Publisher: Elsevier BV
Date: 09-2017
Publisher: Oxford University Press (OUP)
Date: 09-03-2013
DOI: 10.1093/GJI/GGT064
Publisher: Elsevier BV
Date: 04-2020
Publisher: Springer Science and Business Media LLC
Date: 07-07-2012
Publisher: Copernicus GmbH
Date: 09-12-2016
DOI: 10.5194/TC-2016-269
Abstract: Abstract. Mass balance changes of the Antarctic ice sheet are of significant interest due to its sensitivity to climatic changes and its contribution to changes in global sea level. While regional climate models successfully estimate mass input due to snowfall, it remains difficult to estimate the amount of mass loss due to ice dynamic processes. It's often been assumed that changes in ice dynamic rates only need to be considered when assessing long term ice sheet mass balance however, two decades of satellite altimetry observations reveal that the Antarctic ice sheet changes unexpectedly and much more dynamically than previously expected. Despite available estimates on ice dynamic rates obtained from radar altimetry, information about changes in ice dynamic rates are still limited, especially in East Antarctica. Without understanding ice dynamic rates it is not possible to properly assess changes in ice sheet mass balance, surface elevation or to develop ice sheet models. In this study we investigate the possibility of estimating ice dynamic rates by removing modelled rates of surface mass balance, firn compaction and bedrock uplift from satellite altimetry and gravity observations. With similar rates of ice discharge acquired from two different satellite missions we show that it is possible to obtain an approximation of ice dynamic rates by combining altimetry and gravity observations. Thus, surface elevation changes due to surface mass balance, firn compaction and ice dynamic rates can be modelled and correlate with observed elevation changes from satellite altimetry.
Publisher: American Geophysical Union (AGU)
Date: 03-2017
DOI: 10.1002/2016WR019641
Publisher: American Chemical Society (ACS)
Date: 17-07-2017
Publisher: American Geophysical Union (AGU)
Date: 07-07-2011
DOI: 10.1029/2011GL047860
Publisher: Springer Science and Business Media LLC
Date: 13-11-2010
Publisher: Springer Science and Business Media LLC
Date: 07-2011
Publisher: American Geophysical Union (AGU)
Date: 02-2022
DOI: 10.1029/2021JB022489
Abstract: Several different basis functions have been used to represent the Earth's gravity field in order to generate estimates of mass variations on Earth from the analysis of data of the Gravity Recovery and Climate Experiment ( grace ) and its successor grace Follow‐On missions, including spherical harmonics, mass concentration elements (mascons) and slepian functions. Each approach depends inherently upon accurate modeling of the orbits of the pair of satellites as they revolve around the Earth, so that the observations of inter‐satellite changes in range (or, more specifically, range rate) can be exploited to identify mass variations. We have developed software using a classical orbit modeling approach, mascons and 24‐hr orbit integration, to estimate simultaneously corrections to orbital parameters and the temporal gravity field from grace data. Rather than using the range rate, we use the range acceleration as the inter‐satellite observable as it aids in localizing the mass variations. Level‐1 B range acceleration observations contain high levels of high‐frequency noise that inhibits their usefulness for this purpose. Instead, we generate range acceleration observations by numerical differentiation of the Level‐1B range rate prefit residuals. Simulations show that the gravity signal is not attenuated in this process. Our monthly estimates of mass anomalies from grace data (2003–2016) agree well with previous studies, both spatially and temporally. When converted to spherical harmonics our time series of C 2,0 , derived from grace data alone, are close to the independent estimates from satellite laser ranging, but the overall solution is improved by substituting the SLR C 2,0 .
Publisher: Springer Science and Business Media LLC
Date: 08-2017
Publisher: American Geophysical Union (AGU)
Date: 28-08-2017
DOI: 10.1002/2017GL074776
Publisher: EDP Sciences
Date: 11-2019
DOI: 10.1051/M2AN/2019044
Abstract: In this paper we propose a stable and robust strategy to approximate the 3D incompressible hydrostatic Euler and Navier–Stokes systems with free surface. Compared to shallow water approximation of the Navier–Stokes system, the idea is to use a Galerkin type approximation of the velocity field with piecewise constant basis functions in order to obtain an accurate description of the vertical profile of the horizontal velocity. Such a strategy has several advantages. It allows to rewrite the Navier–Stokes equations under the form of a system of conservation laws with source terms, the easy handling of the free surface, which does not require moving meshes, the possibility to take advantage of robust and accurate numerical techniques developed in extensive amount for Shallow Water type systems. Compared to previous works of some of the authors, the three dimensional case is studied in this paper. We show that the model admits a kinetic interpretation including the vertical exchanges terms, and we use this result to formulate a robust finite volume scheme for its numerical approximation. All the aspects of the discrete scheme (fluxes, boundary conditions, ...) are completely described and the stability properties of the proposed numerical scheme (well-balancing, positivity of the water depth, ...) are discussed. We validate the model and the discrete scheme with some numerical academic ex les (3D non stationary analytical solutions) and illustrate the capability of the discrete model to reproduce realistic tsunami waves propagation, tsunami runup and complex 3D hydrodynamics in a raceway.
Publisher: Oxford University Press (OUP)
Date: 10-2012
No related grants have been discovered for Sebastien Allgeyer.