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1. Ambient seismic noise imaging of the lowermost mantle beneath the North Atlantic Ocean

Author

Pierre Boué, Lise Retailleau, Michel Campillo, Lei Li, Observatoire Volcanologique du Piton de la Fournaise (OVPF), Institut de Physique du Globe de Paris, Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Grenoble Alpes (UGA)-Université Gustave Eiffel-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Institut de Physique du Globe de Paris (IPG Paris), Department of Geophysics [Stanford], Stanford EARTH, Stanford University-Stanford University, Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), and The data set was downloaded and processed using python and the seismological community scientific library obspy (Krischer et al. 2015). The figures were produced using Python and MATLAB and the Python module basemap was used to produce the map. The facilities of IRIS Data ervices, and specifically the IRIS Data Management Center, were used for access to waveforms, related metadata, and/or derived products used in this study. IRIS Data Downloaded from https://academic.oup.com/gji/article-abstract/222/2/1339/5827640 by CNRS user on 23 June 2020Services are funded through the Seismological Facilities for the Advancement of Geoscience (SAGE)Award of theNational Science Foundation under Cooperative Support Agreement EAR-1851048.The computation of the correlation functions presented in this paper was performed performed using the GRICAD infrastructure (https://gricad.univ-grenoble-alpes.f r), which is partly supported by the Equip@Meso project (reference ANR-10-EQPX-29–01) of the programme Investissements d’Avenir supervised by the Agence Nationale pour la Recherche. This work has been supported by a grant from Labex OSUG@2020 (Investissements d’avenir—ANR10 LABX56) and Fondation Simone et Cino Del Duca, Institut de France (Prix scientifique 2013). We acknowledge the support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grantagreement No 742335, F-IMAGE). The research of LR was supported by Pacific Gas and Electric. We thank K. Schaukowitch and the Hume centre for writing and speaking at Stanford for useful comments that helped us to improve the manuscript. We thank the Editor, Michael Ritzwoller, St´ephanie Durand and two anonymousreviewers for their comments and suggestions which helped to improve the quality of this paper

Subjects
Composition and structure of the mantle, Seismic noise, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Frequency band, Body waves, Cosmic microwave background, body waves, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Physics::Geophysics, Core-Mantle-Boundary, Geochemistry and Petrology, Time-series analysis, Core–mantle boundary, 14. Life underwater, Atlantic Ocean, 0105 earth and related environmental sciences, Ambient noise correlations, Microseism, Reflectivity, Geophysics, 13. Climate action, Seismology, Geology
Abstract

SUMMARY Body waves can be extracted from correlation functions computed from seismic records even at teleseismic distances. Here we use P and PcP waves from the secondary microseism frequency band that are propagating between Europe and the Eastern United States to image the core–mantle boundary (CMB) and D” structure beneath the North Atlantic. This study presents the first 3-D image of the lower mantle obtained from ocean-generated microseism data. Robustness of our results is evaluated by comparing images produced by propagation in both directions. Our observations reveal complex patterns of lateral and vertical variations of P-wave reflectivity with a particularly strong anomaly extending upward in the lower mantle up to 2600 km deep. We compare these results with synthetic data and associate this anomaly to a Vp velocity increase above the CMB. Our image aims at promoting the study of the lower mantle with microseism noise excitations.

Published
2020
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2. Acceleration of the southern African easterly jet driven by the radiative effect of biomass burning aerosols and its impact on transport during AEROCLO-sA

Author

Jean-Pierre Chaboureau, Laurent Labbouz, Cyrille Flamant, Alma Hodzic, Laboratoire d'aérologie (LAERO), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), National Center for Atmospheric Research [Boulder] (NCAR), and Computer resources for running Meso-NH were allocated by GENCI through project 90569. We thank the PIs Brent Holben, Jens Redemann, Carlos Ribeiro, Nichola Knox and Stuart Piketh, as well as their staff, for establishing and maintaining the AERONET sites used in this investigation. Jean-Pierre Chaboureau thanks NCAR/ACOM for the visitor grant. Laurent Labbouz received a CNES postdoctoral fellowship. We thank the anonymous reviewers for their comments, which helped to improve the overall quality of the paper. The AEROCLO-sA project was supported by the French National Research Agency under grant agreement no. ANR-15-CE01-0014-01, the French national program LEFE/INSU, the Programme national de Télédetection Spatiale (PNTS) under grant no. PNTS-2016-14, the French National Agency for Space Studies (CNES), and the South African National Research Foundation (NRF) under grant UID 105958. The research leading to these results has received funding from the European Union's 7th Framework Programme (FP7/2014-2018) under EUFAR2 contract no. 312609. Airborne data were obtained using the aircraft managed by Safire, the French facility for airborne research, an infrastructure of the French National Center for Scientific Research (CNRS), Météo-France, and the French National Center for Space Studies (CNES). The strong diplomatic assistance of the French Embassy in Namibia, the administrative support of the Service Partnership and Valorisation of the Regional Delegation of the Paris–Villejuif region of the CNRS, and the cooperation of the Namibian National Commission on Research, Science and Technology (NCRST) were invaluable to make the project happen. The support of the aviation authorities is acknowledged. The AEROCLO-sA project would not have been successful without the endless efforts of all the research scientists and engineers involved in its preparation, often behind the scenes. Their support and enthusiasm are sincerely appreciated.

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Atmospheric Science, Astrophysics::Galaxy Astrophysics, Physics::Atmospheric and Oceanic Physics, Physics::Geophysics
Abstract

The direct and semi-direct radiative effects of biomass burning aerosols (BBAs) are investigated over southern Africa and the southeastern Atlantic during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) field campaign in September 2017. A reference convection-permitting simulation has been performed using the Meso-NH model with an online dust emission scheme, a strongly absorbing BBA tracer emitted using the daily Global Fire Emissions Database and online-computed backward Lagrangian trajectories. The simulation captures both the aerosol optical depth and the vertical distribution of aerosols as observed from airborne and spaceborne lidars. The occurrence of stratocumulus over the southeastern Atlantic, deep convective clouds over equatorial Africa and the large-scale circulation are all reproduced by the model. If the radiative effects of BBA are omitted in the model, we show that (i) the smoke plume is too low in altitude, (ii) the low-cloud cover is too weak, (iii) the deep convective activity is too frequent but not intense enough, (iv) the Benguela low-level jet is too strong, and (v) the southern African easterly jet is too weak. The Lagrangian analysis indicates that the radiative effect of BBA leads to the transport of BBA to higher altitudes, farther southwest and with a stronger diurnal oscillation. The higher smoke plume altitude can be explained by a combination of three factors: increased upward motion induced by the stronger southern African easterly jet, self-lofting of BBA and reduced subsidence associated with less frequent deep convective activity over western equatorial Africa.

Published
2022
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3. A laser tomograph technique for ice core stratigraphy analysis

Author

Morimasa, Takata, Yoshiyuki, Fujii, Scientific Paper, The Graduate University for Advanced Studies, and National Institute of Polar Research

Subjects
Computer Science::Computer Vision and Pattern Recognition, Physics::Atmospheric and Oceanic Physics, Physics::Geophysics
Abstract

We have developed a laser tomograph system to analyze the detailed stratigraphic structure of ice core samples. We use a He-Ne laser as the light source and a CCD camera as a detector of a scattered image of air bubbles in ice. An image of air bubble distribution in the ice sample is obtained by image analysis of the scattered images. Two different algorithms are employed in the image analysis in order to improve the laser tomograph images. A profile of pore ratios obtained by using optimum conditions and algorithms for the analysis shows a good correlation of 0.80 with the actual pore ratio profile.

Published
2000

4. NEUTRON SCATTERING MEASUREMENTS ON VOSTOK ANTARCTIC ICE

Author

Hiroshi, FUKAZAWA, Shinji, MAE, Susumu, IKEDA, Vladimir Ya., LIPENKOV, Scientific Paper, Department of Applied Physics, Faculty of Engineering, Hokkaido University, Institute of Materials Structure Science, High Energy Accelerator Research Organization, and The Arctic and Antarctic Research Institute

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Earth and Planetary Astrophysics, Nuclear Experiment, Physics::Atmospheric and Oceanic Physics, Physics::Geophysics
Abstract

We measured the incoherent inelastic neutron scattering (IINS) of Vostok Antarctic ice in order to investigate the arrangement of protons in the ice and to verify the proton ordering in Antarctic ice previously observed by IINS measurements on Dome Fuji Antarctic ice (FUKAZAWA et al., Chem. Phys. Lett., 294,554,1998a). The IINS spectrum of Vostok ice at 500m in depth has a peak at 19 meV in the region of translational lattice vibrations, while the peak in Vostok ice at 2452m in depth is much lower. Ice XI with a proton-ordered arrangement has a sharp peak at 19meV, while ordinary ice (ice Ih) with a proton-disordered arrangement does not have such a peak. These results of analysis of the IINS spectra indicate that Vostok ice at 500m in depth has a proton-ordered arrangement.

Published
1999

5. INFLUENCES OF ARCTIC OZONE HOLE ON THE STRATOSPHERIC GENERAL CIRCULATION

Author

Toshihiko, HIROOKA, Toshihiko, NISHIYOSHI, Shingo, WATANABE, Saburo, MIYAHARA, Scientific Paper, and Department of Earth and Planetary Sciences, Kyushu University

Subjects
Astrophysics::Earth and Planetary Astrophysics, Physics::Atmospheric and Oceanic Physics, Physics::Geophysics
Abstract

Numerical experiments are performed for four years to estimate radiative and dynamical influences of the "Arctic ozone hole" on the stratospheric general circulation by using a general circulation model developed at Kyushu University. The model includes simplified ozone photochemistry interactively coupled with radiation and dynamics. The resultant temperature structure consists of cooling of about 6K in the polar lower stratosphere and warming of about 8K in the polar upper stratosphere, which intensifies the polar night jet by about 9ms^. The cooling is caused by reduction of downward motion as well as decrease of solar UV heating due to ozone depletion, while the warming is caused by dynamical heating due to enhancement of downward motion. The results imply that the feedback mechanism may strengthen the ozone hole itself.

Published
1999

6. Statistics of whistler mode waves in the outer radiation belt: Cluster STAFF-SA measurements

Author

Michael A. Balikhin, Hugo Breuillard, Didier Mourenas, Oleksiy Agapitov, G. Rolland, Vladimir Krasnoselskikh, Yuri V. Khotyaintsev, Anton Artemyev, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Swedish Institute of Space Physics [Kiruna] (IRF), Centre d'Études de Limeil-Valenton (CEA-DAM), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Department of Automatic Control and Systems Engineering, University of Sheffield [Sheffield], Centre National d'Études Spatiales [Toulouse] (CNES), for their assistance in evaluating this paper. This work was supported by CNES through the grant 'Modeles d’ondes' and Cluster Co-I DWP.Swedish Research Council, grant 2007-4377, and European Project: 284520,EC:FP7:SPA,FP7-SPACE-2011-1,MAARBLE(2012)

Subjects
Physics, Hiss, 010504 meteorology & atmospheric sciences, Whistler, Wave propagation, 01 natural sciences, Physics::Geophysics, L-shell, symbols.namesake, Geophysics, Amplitude, Earth's magnetic field, Space and Planetary Science, Surface wave, [SDU]Sciences of the Universe [physics], Van Allen radiation belt, 0103 physical sciences, Statistics, Physics::Space Physics, symbols, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

International audience; [1] ELF/VLF waves play a crucial role in the dynamics of the radiation belts and are partly responsible for the main losses and the acceleration of energetic electrons. Modeling wave-particle interactions requires detailed information of wave amplitudes and wave normal distribution over L-shells and over magnetic latitudes for different geomagnetic activity conditions. We performed a statistical study of ELF/VLF emissions using wave measurements in the whistler frequency range for 10 years (2001–2010) aboard Cluster spacecraft. We utilized data from the STAFF-SA experiment, which spans the frequency range from 8 Hz to 4 kHz. We present distributions of wave magnetic and electric field amplitudes and wave normal directions as functions of magnetic latitude, magnetic local time, L-shell, and geomagnetic activity. We show that wave normals are directed approximately along the background magnetic field (with the mean value of  — the angle between the wave normal and the background magnetic field, about 10 ı –15 ı) in the vicinity of the geomagnetic equator. The distribution changes with magnetic latitude: Plasmaspheric hiss normal angles increase with latitude to quasi-perpendicular direction at 35 ı –40 ı where hiss can be reflected; lower band chorus are observed as two wave populations: One population of wave normals tends toward the resonance cone and at latitudes of around 35 ı –45 ı wave normals become nearly perpendicular to the magnetic field; the other part remains quasi-parallel at latitudes up to 30 ı. The observed angular distribution is significantly different from Gaussian, and the width of the distribution increases with latitude. Due to the rapid increase of  , the wave mode becomes quasi-electrostatic, and the corresponding electric field increases with latitude and has a maximum near 30 ı. The magnetic field amplitude of the chorus in the day sector has a minimum at the magnetic equator but increases rapidly with latitude with a local maximum near 12 ı –15 ı. The wave magnetic field maximum is observed in the night sector at L > 7 during low geomagnetic activity (at L 5 for K p > 3). Our results confirm the strong dependence of wave amplitude on geomagnetic activity found in earlier studies. (2013), Statistics of whistler-mode waves in the outer radiation belt: Cluster STAFF-SA measurements

Published
2013
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