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21 results on '"Christophe Hoareau"'

1. Optimal electrode coverage based on a new criterion for piezoelectric energy harvesters

Author

Lan Shang, Christophe Hoareau, and Andreas Zilian

Subjects
Multidisciplinaire, généralités & autres [C99] [Ingénierie, informatique & technologie], Fuel Technology, Nuclear Energy and Engineering, Piezoelectric energy harvesting, Renewable Energy, Sustainability and the Environment, Multidisciplinary, general & others [C99] [Engineering, computing & technology], Energy Engineering and Power Technology, Electrode coverage optimization, Design criterion, Beam cross-section rotation
Abstract

Piezoelectric energy harvesters (PEHs) are a promising alternative to conventional electrochemical batteries with the advantage of being self-powered and maintenance-free, but their application is severely restricted by the low electric power output. It has been reported that the power output of PEHs can be enhanced by well-designed electrode coverage. A common design criterion for beam-like PEHs is based on the strain node to avoid electrode charge cancellation. This criterion, however, is not feasible for PEHs subject to complex spatio-temporal excitation patterns, where strain nodes change their position. This work proposes a new design criterion for optimal electrode coverage of beam-like PEHs based on the closed-form solution of the circuit equation that expresses voltage as a function of the beam’s dynamic response, specifically the cross-section rotation. The new criterion maximizes the averaged curvature of the beam segment covered by the electrode using data on the instantaneous rotation field. The improved physical significance and reliability of the presented criterion are discussed. The associated electrode optimization procedure is then exemplified for PEHs driven by fluid flow, which helps to realize a complex excitation pattern. Two numerical studies, both including a variety of combinations of fluid densities and inlet velocities, are performed to demonstrate that an optimal electrode configuration can be obtained with the proposed criterion. Comparison of different electrode configurations in above studies finally leads to useful conclusions on the power output and electrode configuration.

Published
2023

2. Modeling and simulation of thin-walled piezoelectric energy harvesters immersed in flow using monolithic fluid–structure interaction

Author

Lan Shang, Christophe Hoareau, and Andreas Zilian

Subjects
Multidisciplinaire, généralités & autres [C99] [Ingénierie, informatique & technologie], Applied Mathematics, Multidisciplinary, general & others [C99] [Engineering, computing & technology], General Engineering, Computer Graphics and Computer-Aided Design, Analysis
Published
2022
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4. Nonlinear equilibrium of partially liquid-filled tanks: A finite element/level-set method to handle hydrostatic follower forces

Author

Christophe Hoareau, Jean-François Deü, Laboratoire de Mécanique des Structures et des Systèmes Couplés (LMSSC), and Conservatoire National des Arts et Métiers [CNAM] (CNAM)

Subjects
Level set method, Applied Mathematics, Mechanical Engineering, Tangent, 02 engineering and technology, Mechanics, 021001 nanoscience & nanotechnology, Finite element method, Numerical integration, law.invention, Physics::Fluid Dynamics, [SPI]Engineering Sciences [physics], 020303 mechanical engineering & transports, 0203 mechanical engineering, Rate of convergence, Mechanics of Materials, Inviscid flow, law, [SPI.MECA.STRU]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], Compressibility, Hydrostatic equilibrium, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS, Mathematics
Abstract

This paper deals with the nonlinear finite element computation of the prestressed state of structures partially filled with an incompressible inviscid liquid. The fluid is modeled by hydrostatic follower forces such that no volumetric fluid mesh is needed. Large deformations are taken into account and lead to the fluid height variation of the wetted surface to satisfy the fluid volume conservation. The main originality of this work lies on the use of a level-set approach to handle numerical integration on the fluid–structure interface. The method is developed on 3D problems considering a finite element quadratic mesh. Various numerical examples are computed using a Newton–Raphson algorithm and a quadratic convergence rate is reached by using consistent tangent stiffness operators.

Published
2019
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5. Towards an automatic lidar cirrus cloud retrieval for climate studies

Author

Eliane G. Larroza, Riad Bourayou, Christophe Hoareau, Walter M. Nakaema, Philippe Keckhut, Eduardo Landulfo, Center for Lasers and Applications [São Paulo] (CLA), Instituto de Pesquisas Energéticas e Nucleares [São Paulo] (IPEN/CNEN-SP), Universidade de São Paulo = University of São Paulo (USP)-Comissão National de Energia Nuclear (CNEN)-Universidade de São Paulo = University of São Paulo (USP)-Comissão National de Energia Nuclear (CNEN), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut Pierre-Simon-Laplace (IPSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Universidade de São Paulo = University of São Paulo (USP)-Comissão National de Energia Nuclear (CNEN), STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Comissão National de Energia Nuclear (CNEN)-Universidade de São Paulo (USP)-Comissão National de Energia Nuclear (CNEN)-Universidade de São Paulo (USP), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), and Comissão National de Energia Nuclear (CNEN)-Universidade de São Paulo (USP)

Subjects
Atmospheric Science, Meteorology, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Cloud computing, 01 natural sciences, 010309 optics, 0103 physical sciences, lcsh:TA170-171, Air mass, Remote sensing, 0105 earth and related environmental sciences, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Ice crystals, Microphysics, business.industry, Orientation (computer vision), lcsh:TA715-787, lcsh:Earthwork. Foundations, lcsh:Environmental engineering, Lidar, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Trajectory, Environmental science, Cirrus, business
Abstract

This paper presents a methodology to calculate lidar ratios for distinct cirrus clouds that has been developed and implemented for a site located in the Southern Hemisphere. The cirrus cloud lidar data processing aims to consider a large cloud variability and cirrus cloud monitoring through a robust retrieval process. Among cirrus features estimates for complex scenes that lidar systems can provide, we highlight cloud geometrical information and extinction-to-backscatter ratio (known as lidar ratio or LR). In general, direct information on cirrus cloud microphysics is difficult to derive because LR depends on the presence of ice crystals and their properties such as shape, size, composition and orientation of particles. An iterative process to derive a stable LR value has been proposed. One of the keys is to restrict the analysis to conditions allowing accurate multilayer events. This method uses nonparametric statistical approaches to identify stationary periods according to cloud features and variability. Measurements performed in the region of the metropolitan city of São Paulo (MSP) have been used to implement and test the methodology developed for cirrus cloud characterization. Good results are represented by examining specific cases with multilayer cirrus cloud occurrence. In addition to the geometrical parameters obtained, cirrus LR values were calculated for a single day ranging from 19 ± 01 sr to 74 ± 13 sr for 2 observed layers. This large difference in LR can indicate a mixture of ice crystal particles with different sizes and shapes in both layers of the cirrus clouds. Trajectory analyses indicate that both of these cloud layers can be associated with different air mass and should be considered as 2 distinct clouds in climatology.

Published
2018
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6. Non-linear finite element analysis of an elastic structure loaded by hydrostatic following forces

Author

Christophe Hoareau, Jean-François Deü, Laboratoire de Mécanique des Structures et des Systèmes Couplés (LMSSC), and Conservatoire National des Arts et Métiers [CNAM] (CNAM)

Subjects
Engineering, Mechanical equilibrium, Discretization, Iterative method, business.industry, Tangent, 02 engineering and technology, General Medicine, Mechanics, [SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph], 01 natural sciences, Finite element method, law.invention, 020303 mechanical engineering & transports, Classical mechanics, 0203 mechanical engineering, Inviscid flow, law, Free surface, 0103 physical sciences, Hydrostatic equilibrium, business, 010301 acoustics, ComputingMilieux_MISCELLANEOUS
Abstract

This study deals with the non-linear finite element computation of thin flexible structures loaded by hydrostatic forces due to the presence of an internal liquid at rest. In aerospace application, the dynamic behaviour of structures containing an inviscid incompressible fluid (i.e. launcher with liquid propellant, tank of satellite, etc.) is generally computed considering an equilibrium state resulting from a linear fluid-structure interaction problem. It is important to note that in this case, the gravity plays an important role in vibrations and the so called elastogravity operator should be taken into account [1,2]. In the present work, we consider the large deformation behavior of a structure loaded by hydrostatic follower forces in order to obtain an accurate static equilibrium state. The solution is computed using a Newton-Raphson algorithm considering the geometrical and material tangent stiffness matrices as well as the contribution of the follower forces [3]. Those linearized operators of the iterative algorithm are used to compute the dependancy between the incremental horizontal level of the free surface, under the fluid volume conservation constraint [4]. Special attention is paid to the finite element discretization of the wetted surface, considering a level-set method [6,7]. Some numerical examples are analyzed to show the efficiency of the proposed approach.

Published
2017
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7. Effects of solar activity on noise in CALIOP profiles above the South Atlantic Anomaly

Author

G. Cesana, M. Reverdy, Hélène Chepfer, Vincent Noel, Christophe Hoareau, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Atmospheric Science, 010504 meteorology & atmospheric sciences, lcsh:TA715-787, Lag, lcsh:Earthwork. Foundations, Atmospheric sciences, 01 natural sciences, 010305 fluids & plasmas, South Atlantic Anomaly, lcsh:Environmental engineering, Geographic distribution, Lidar, 13. Climate action, 0103 physical sciences, Environmental science, Upwelling, lcsh:TA170-171, Particle flux, Noise (radio), 0105 earth and related environmental sciences
Abstract

We show that nighttime dark noise measurements from the spaceborne lidar CALIOP contain valuable information about the evolution of upwelling high-energy radiation levels. Above the South Atlantic Anomaly (SAA), CALIOP dark noise levels fluctuate by ±6% between 2006 and 2013, and follow the known anticorrelation of local particle flux with the 11-year cycle of solar activity (with a 1-year lag). By analyzing the geographic distribution of noisy profiles, we are able to reproduce known findings about the SAA region. Over the considered period, it shifts westward by 0.3° year−1, and changes in size by 6° meridionally and 2° zonally, becoming larger with weaker solar activity. All results are in strong agreement with previous works. We predict SAA noise levels will increase anew after 2014, and will affect future spaceborne lidar missions most near 2020.

Published
2014
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8. Maïdo observatory: a new high-altitude station facility at Reunion Island (21° S, 55° E) for long-term atmospheric remote sensing and in situ measurements

Author

Françoise Posny, Yann Courcoux, F. Desmet, Karine Sellegri, Robert Delmas, M. De Mazière, Thierry Portafaix, Alain Hauchecorne, Jean Sciare, J. Leclair de Bellevue, Franck Gabarrot, S. Godin Beekmann, Guillaume Payen, Jean-Luc Baray, Aurélie Colomb, C. Vuillemin, Davide Dionisi, Valentin Duflot, Jacques Porteneuve, Jean-Pierre Cammas, T. Gaudo, Christelle Barthe, Philippe Ricaud, Pierre Tulet, Jean-Marc Metzger, Hélène Vérèmes, Abdel Abchiche, Michel Ramonet, Christian Hermans, Philippe Keckhut, Christophe Hoareau, Laboratoire de l'Atmosphère et des Cyclones (LACy), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Météo-France, Observatoire des Sciences de l'Univers de La Réunion (OSU-Réunion), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR), Laboratoire de Météorologie Physique (LaMP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Spectroscopie de l'atmosphère, Service de Chimie Quantique et Photophysique, Université libre de Bruxelles (ULB), Laboratoire de météorologie physique (LaMP), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), ICOS-RAMCES (ICOS-RAMCES), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Chimie Atmosphérique Expérimentale (CAE), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Division technique INSU/SDU (DTI), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-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)-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 -Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Météo France, Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), and Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, lcsh:TA715-787, lcsh:Earthwork. Foundations, Climate change, Subtropics, 01 natural sciences, lcsh:Environmental engineering, 010309 optics, Troposphere, Lidar, Observatory, 0103 physical sciences, Environmental science, 14. Life underwater, lcsh:TA170-171, Sociologie politique, Southern Hemisphere, Stratosphere, Sea level, 0105 earth and related environmental sciences, Remote sensing
Abstract

Since the nineties, atmospheric measurement systems have been deployed at Reunion Island, mainly for monitoring the atmospheric composition in the framework of NDSC/NDACC (Network for the Detection of Stratospheric< /i> Change/Network for the Detection of Atmospheric Composition Change). The location of Reunion Island presents a great interest because there are very few multi-instrumented stations in the tropics and particularly in the southern hemisphere. In 2012, a new observatory was commissioned in Maïdo at 2200 m above sea level: it hosts various instruments for atmospheric measurements, including lidar systems, spectro-radiometers and in situ gas and aerosol measurements. This new high-altitude Maïdo station provides an opportunity: 1. to improve the performance of the optical instruments above the marine boundary layer, and to open new perspectives on upper troposphere and lower stratosphere studies; 2. to develop in situ measurements of the atmospheric composition for climate change surveys, in a reference site in the tropical/subtropical region of the southern hemisphere; 3. to offer trans-national access to host experiments or measurement campaigns for focused process studies. © 2013 Author(s)., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2013
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9. Modélisation éléments finis non-linéaire de réservoirs élastiques soumis à une charge suiveuse hydrostatique

Author

Christophe Hoareau, Jean-François Deü, Sciencesconf.org, CCSD, Laboratoire de Mécanique des Structures et des Systèmes Couplés (LMSSC), Conservatoire National des Arts et Métiers [CNAM] (CNAM), and Université Paris-Saclay

Subjects
formulation lagrangienne totale, grands déplacements, éléments finis, forces suiveuses hydrostatiques, [SPI.MECA.STRU] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], remaillage, ligne de niveau, interaction fluide-structure, [SPI.MECA.STRU]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of the structures [physics.class-ph]
Abstract

International audience; Nous développons une modélisation éléments finis (EF) non-linéaire quasi-statique d’un réservoir flexible soumis à des forces hydrostatiques dues à la présence d’un liquide interne incompressible non visqueux. Ce problème non-linéaire est résolu grâce à une méthode itérative de type Newton-Raphson, sans maillage du fluide. Nous montrons qu’une attention particulière doit être portée à la discrétisation spatiale de la structure et de la surface mouillée. Deux méthodes seront envisagées : une stratégie de remaillage et une stratégie de découpage des éléments par une méthode de ligne de niveau.

Published
2017

10. Methodology for Water Monitoring in the Upper Troposphere with Raman Lidar at the Haute-Provence Observatory

Author

Christophe Hoareau, Alain Sarkissian, Jean-Luc Baray, Georges Durry, Philippe Keckhut, STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de l'Atmosphère et des Cyclones (LACy), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Météo France, Observatoire des Sciences de l'Univers de La Réunion (OSU-Réunion), Université de La Réunion (UR)-Institut national des sciences de l'Univers (INSU - CNRS), Groupe de spectrométrie moléculaire et atmosphérique (GSMA), Université de Reims Champagne-Ardenne (URCA)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Météo-France, Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR), Alarcon, Nicolas, and Agence de l'environnement et de la maîtrise de l'énergie (ADEME)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, Ocean Engineering, 01 natural sciences, [PHYS.PHYS.PHYS-AO-PH] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], law.invention, Aerosol, 010309 optics, Troposphere, Lidar, 13. Climate action, law, Observatory, 0103 physical sciences, Radiosonde, Calibration, Environmental science, Water vapor, Zenith, 0105 earth and related environmental sciences, Remote sensing
Abstract

A Raman water vapor lidar has been developed at the Haute-Provence Observatory to study the distribution of water in the upper troposphere and its long-term evolution. Some investigations have been proposed and described to ensure a pertinent monitoring of water vapor in the upper troposphere. A new method to take into account the geophysical variability for time integration processes has been developed based on the stationarity of water vapor. Successive measurements, considered as independent, have been used to retrieve H2O profiles that were recorded during the same nighttimes over a few hours. Various calibration methods, including zenith clear-sky observation, standard meteorological radiosondes, and total water vapor column, have been investigated. A method to evaluate these calibration techniques has been proposed based on the variance weakening. For the lidar at the Haute-Provence Observatory, the calibration based on the total water vapor column appears to be the optimum method. Radiosondes also give comparable results, but do not allow lidar to be independent. The clear-sky zenith observation is an original technique, and seems to accurately identify discontinuities. However, it appears to be less reliable, based on the variance investigation, than the two others. It is also sensitive to aerosol loading, which is also expected to vary with time.

Published
2009
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11. Remote sensing ice supersaturation inside and near cirrusclouds: a case study in the subtropics

Author

M. Reverdy, Hélène Chepfer, Marjolaine Chiriaco, Jérôme Vidot, Christophe Hoareau, Vincent Noel, Sophie Bastin, G. Cesana, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Laboratoire d'aérologie (LAERO), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Centre de Météorologie Spatiale, Météo France, SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), 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), Direction des Opérations pour la Prévision (DIROP), and Météo-France -Météo-France

Subjects
Atmospheric Science, Supersaturation, 010504 meteorology & atmospheric sciences, Meteorology, Atmospheric wave, supersaturation, cirrus, Subtropics, 010501 environmental sciences, [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology, Atmospheric sciences, 01 natural sciences, Lidar, 13. Climate action, Raman lidar, water vapor, Environmental science, Relative humidity, Cirrus, Satellite, subtropics, Water vapor, 0105 earth and related environmental sciences, Remote sensing
Abstract

International audience; Combining vertically resolved lidar retrievals of water vapor and cloud detection, we document a 2-day subtropical cirrus case study over La Réunion (20.9∘S–55.5∘E) in March 2005, focusing on the conditions of ice supersaturation inside and near the observed cloud. Using satellite observations, we describe the synoptic conditions leading to cloud formation. Supersaturation occurs 25% of the time within the cirrus, up to 35% in its middle segment, where relative humidity goes beyond 150%. In clear-sky areas, relative humidity stays consistentlylow, especially in profiles without clouds. High-troposphere atmospheric waves could initiate the formation of supersaturation conditions, especially on 16 March.

Published
2016
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12. Effects of solar activity and geomagnetic field on noise in CALIOP profiles above the South Atlantic Anomaly

Author

G. Cesana, M. Reverdy, Vincent Noel, Christophe Hoareau, and H. Chepfer

Subjects
Earth's magnetic field, Meteorology, Environmental science, Geophysics, Noise (radio), South Atlantic Anomaly
Abstract

By documenting noise levels in 6.5 yr of nighttime measurements by the spaceborne lidar CALIOP above the South Atlantic Anomaly (SAA), we show they contain information about the evolution of upwelling high-energy radiation levels in the area. We find the amount of noisy profiles is influenced by the 11 yr cycle of solar activity, fluctuates by ±5% between 2006 and 2013, and is anticorrelated with solar activity with a 1 yr lag. The size of the SAA grows as solar activity decreases, and an overall westward shift of the SAA region is detectable. We predict SAA noise levels will increase anew after 2014, and will affect future spaceborne lidar missions most near 2020. In other areas, supposedly unaffected by incoming sunlight, nighttime noise levels are much weaker but follow the same 11 yr cycle, superimposed with a one-year cycle that affects both hemispheres similarly and could be attributed to geomagnetic activity.

Published
2013
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13. A decadal cirrus clouds climatology from ground-based and spaceborne lidars above the south of France (43.9° N-5.7° E)

Author

Hélène Chepfer, Christophe Hoareau, Philippe Keckhut, Jean-Luc Baray, Vincent Noel, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de l'Atmosphère et des Cyclones (LACy), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Météo-France

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Atmospheric Science, 010504 meteorology & atmospheric sciences, Cloud cover, [SDE.MCG]Environmental Sciences/Global Changes, Atmospheric sciences, 01 natural sciences, Mean difference, lcsh:QC1-999, 010309 optics, Troposphere, lcsh:Chemistry, Lidar, lcsh:QD1-999, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Middle latitudes, Climatology, 0103 physical sciences, Environmental science, Lidar data, Cirrus, Cirrus cloud, lcsh:Physics, 0105 earth and related environmental sciences
Abstract

This study provides an analysis of cirrus cloud properties at midlatitude in the southern part of France from ground-based and spaceborne lidars. A climatology of cirrus cloud properties and their evolution over more than 12 yr is presented and compared to other mid-latitude climatological studies. Cirrus clouds occur ~37% of the total observation time and remain quasi-constant across seasons with a variation within ~5% around the mean occurrence. Similar results are obtained from CALIOP and the ground-based lidar, with a mean difference in occurrence of ~5% between both instruments. From the ground-based lidar data, a slight decrease in occurrence of ~3% per decade is observed but found statistically insignificant. Based on a clustering analysis of cirrus cloud parameters, three distinct classes have been identified and investigations concerning their origin are discussed. Properties of these different classes are analysed, showing that thin cirrus in the upper troposphere represent ~50% of cloud cover detected in summer and fall, decreasing by 15–20% for other seasons.

Published
2013
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14. Accuracy assessment of water vapour measurements from in situ and remote sensing techniques during the DEMEVAP 2011 campaign at OHP

Author

Florence Goutail, Alain Sarkissian, Philippe Keckhut, Andrea Pazmino, Diane Tzanos, Guy Tournois, Christophe Hoareau, D. Legain, K. Pipis, Jacques Pelon, Pierre Bosser, Olivier Bock, G. Poujol, Christian Thom, T. Bourcy, Leslie David, LAboratoire de REcherche en Géodésie [Paris] (LAREG), Laboratoire des Sciences et Technologies de l'Information Géographique (LaSTIG), École nationale des sciences géographiques (ENSG), Institut National de l'Information Géographique et Forestière [IGN] (IGN)-Institut National de l'Information Géographique et Forestière [IGN] (IGN)-École nationale des sciences géographiques (ENSG), Institut National de l'Information Géographique et Forestière [IGN] (IGN)-Institut National de l'Information Géographique et Forestière [IGN] (IGN), Institut National de l'Information Géographique et Forestière [IGN] (IGN), Direction des Systèmes d'Observation [Toulouse] (DSO), Météo France, STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), SPACE - LATMOS, Laboratoire d'Opto-électronique et de Micro-Informatique (LOEMI), Observatoire Astronomique de Marseille Provence (OAMP), Institut national des sciences de l'Univers (INSU - CNRS), Météo-France, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-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)-Université Toulouse III - Paul Sabatier (UT3), and 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 -Centre National de la Recherche Scientifique (CNRS)

Subjects
Atmospheric Science, Meteorology, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, 01 natural sciences, law.invention, Sun photometer, 010309 optics, law, 0103 physical sciences, Calibration, lcsh:TA170-171, Remote sensing, 0105 earth and related environmental sciences, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Spectrometer, business.industry, lcsh:TA715-787, lcsh:Earthwork. Foundations, AERONET, lcsh:Environmental engineering, Depth sounding, Lidar, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Global Positioning System, Radiosonde, Environmental science, business
Abstract

The Development of Methodologies for Water Vapour Measurement (DEMEVAP) project aims at assessing and improving humidity sounding techniques and establishing a reference system based on the combination of Raman lidars, ground-based sensors and GPS. Such a system may be used for climate monitoring, radiosonde bias detection and correction, satellite measurement calibration/validation, and mm-level geodetic positioning with Global Navigation Satellite Systems. A field experiment was conducted in September–October 2011 at Observatoire de Haute Provence. Two Raman lidars, a stellar spectrometer (SOPHIE), a differential absorption spectrometer (SAOZ), a sun photometer (AERONET), 5 GPS receivers and 4 types of radiosondes (Vaisala RS92, MODEM M2K2-DC and M10, and Meteolabor Snow-White) participated in the campaign. A total of 26 balloons with multiple radiosondes were flown during 16 clear nights. This paper presents preliminary findings from the analysis of all these datasets. Several classical Raman lidar calibration methods are evaluated which use either Vaisala RS92 measurements, point capacitive humidity measurements, or GPS integrated water vapour (IWV) measurements. A novel method proposed by Bosser et al. (2010) is also tested. It consists in calibrating the lidar measurements during the GPS data processing. The methods achieve a repeatability of 4–5%. A drift in the IGN-LATMOS Raman lidar calibration of 15% over the 45 days of the experiment is evidenced but not yet explained. When this drift is removed, the precision of the calibration factors improves to 2–3%. However, the variations in the absolute calibration factor between methods and types of reference data remain at the level of 7%. The intercomparison of radiosonde measurements shows good agreement between RS92 and Snow-White measurements up to 12 km. An overall dry bias is found in the measurements from both MODEM radiosondes. Investigation of situations with low RH values (

Published
2013
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15. Subgrid-scale cirrus observed by lidar at mid-latitude : variability of the cloud optical depth

Author

Philippe Keckhut, Jean-Marie Perrin, Nadège Montoux, Christophe Hoareau, Jacques Porteneuve, Gérard Thuillier, STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Haute-Provence (OHP), Institut Pythéas (OSU PYTHEAS), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris)

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], 010504 meteorology & atmospheric sciences, Scattering, Advection, subgrid variability, cirrus, cloud optical depth, 01 natural sciences, Light scattering, 010305 fluids & plasmas, Lidar, 13. Climate action, Middle latitudes, 0103 physical sciences, Radiative transfer, General Earth and Planetary Sciences, Cirrus, Optical depth, Geology, Astrophysics::Galaxy Astrophysics, Physics::Atmospheric and Oceanic Physics, lidar, 0105 earth and related environmental sciences, Remote sensing
Abstract

International audience; The temporal variability of the 532-nm optical depth of cirrus clouds observed with a lidar at Observatory of Haute-Provence (43.9°N, 5.7°E, and 683-m altitude), has been analyzed. While advection dominates at the first order, variability of the optical depth on timescales of minutes can be related to spatial fluctuations of cloud properties on typical scales of a few kilometers. Log-normal distributions of the optical depth have been used to model the variability of the cirrus optical depth as observed by lidars. These investigations have been performed for three independent classes of cirrus. The log-normal distribution of the optical depth is applicable to the classes of thin clouds; however, for thick clouds, likely due to successive freezing/defreezing effects, the distribution is rather bimodal. This work compares the effects of visible solar light scattered by inhomogeneous cirrus to effects generated by homogeneous clouds having a constant geometrical thickness using the short-scale lidar observations of optical depth distribution and an analytical approach. In the case of thin cirrus, the scattering of solar light reaching the ground is stronger for inhomogeneous than homogeneous cirrus. In case of thick cirrus, multiple-scattering processes need to be considered. The conclusion is that log-normal distribution of the cirrus optical depth should be considered in any radiative calculation in case of model grids larger than a few kilometers whatever the cirrus type is.

Published
2013
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16. Cirrus crystal fall velocity estimates using the Match method with ground-based lidars: first investigation through a case study

Author

Fernando Congeduti, Christophe Hoareau, Nadège Montoux, Davide Dionisi, Philippe Keckhut, Istituto di Scienze dell'Atmosfera e del Clima (ISAC), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Laboratoire de météorologie physique (LaMP), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), CNR Institute of Atmospheric Sciences and Climate (ISAC), Consiglio Nazionale delle Ricerche [Roma] (CNR), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS), and Consiglio Nazionale delle Ricerche (CNR)

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, lcsh:TA715-787, [SDE.MCG]Environmental Sciences/Global Changes, lcsh:Earthwork. Foundations, 01 natural sciences, lcsh:Environmental engineering, 010309 optics, Troposphere, Lidar, 13. Climate action, Observatory, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, 0103 physical sciences, Range (statistics), Cirrus, lcsh:TA170-171, Tropopause, Adiabatic process, Optical depth, Geology, 0105 earth and related environmental sciences
Abstract

Cirrus ice particle sedimentation velocity (vs) is one of the critical variables for the parameterization of cirrus properties in a global climate model (GCM). In this study a methodology to estimate cirrus properties, such as crystal mean fall speed, through successive lidar measurements is evaluated. This "Match" technique has been applied on cirrus cloud observations and then tested with measurements from two ground-based lidars located in the Mediterranean area. These systems, with similar instrumental characteristics, are installed at the Observatory of Haute Provence (OHP, 43.9° N, 5.7° E) in France and at Rome Tor Vergata (RTV, 41.8° N, 12.6° E) in Italy. At a distance of approximately 600 km, the two lidar stations have provided systematic measurements for several years and are along a typical direction of an air path. A test case of an upper tropospheric cirrus, observed over both sites during the night between 13 and 14 March 2008, has been selected and the feasibility of the Match-cirrus approach investigated through this case. The analysis through lidar principal parameters (vertical location, geometrical thickness and optical depth) reveals a case of a thin sub-visible cirrus (SVC) located around the tropopause. A first range of values for vs (1.4–1.9 cm s−1, consistent with simple-shaped small crystals) has been retrieved with a simplified approach (adiabatic transport and "frozen" microphysical conditions inside the cirrus). The backward trajectory analysis suggests a type of cirrus formed by large-scale transport processes (adiabatic cooling of moist air masses coming from the subtropical area around Mexico gulf), which is characterized by a long atmospheric lifetime and horizontal extension of several hundred km. The analysis of this case study reveals that many uncertainties reduce the confidence of the retrieved estimates of the crystal fall velocity. However, this paper allows for assessing the technique feasibility by identifying the main critical issues for future similar investigations. This study shows that such approach is feasible; however, the methodology should be improved and some directions have been suggested for future campaigns.

Published
2013
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17. Cirrus crystal fall velocity estimates using the Match method with ground-based lidars: a first case study

Author

F. Congeduti, P. Kekchut, N. Montoux, Christophe Hoareau, and D. Dionisi

Subjects
Crystal, Optics, business.industry, Environmental science, Cirrus, business, Match method, Remote sensing
Abstract

Cirrus ice particle sedimentation velocity (vr) is one of the critical variables for the parameterization of cirrus properties in a global climate model (GCM). In this study a methodology to estimate cirrus properties, such as crystal mean fall speed, through successive lidar measurements is evaluated. This "Match" technique has been applied on cirrus cloud observations and then tested with measurements from two ground-based lidars located in the Mediterranean Area. These systems have similar instrumental characteristics, and are operated manually respectively at the Observatory of Haute Provence (OHP, 43.9° N, 5.7° E) in France and at Rome Tor Vergata (RTV, 41.8° N, 12.6° E) in Italy at a distance of approximately 600 km providing systematic measurements since several years. The both sites are along a typical direction of an air path and a test case of an upper tropospheric cirrus, observed over both sites during the night between 13 and 14 of March 2008, has been identified and investigated. The analysis through lidar primarily parameters (cloud shape and vertical location) reveals a case of a thin sub-visible cirrus (SVC) located around the tropopause. The feasibility to estimate crystal fall velocity has been tested and values of 1.4–1.9 cm s−1, consistent with simple-shaped small crystals, have been retrieved. Despite several uncertainties that affect the single-wavelength lidar measurements, sedimentation could be a partial reason for the cirrus property changes (e.g. geometrical thickness and back-scattering profile distribution) observed from one site to the other. The backward trajectory analysis suggests a type of cirrus formed by large-scale transport processes (adiabatic cooling of moist air masses coming from the subtropical area around Mexico gulf), which is characterized by a long atmospheric lifetime and horizontal extension of several hundreds of km. This study shows that such approach can be improved in using closer locations, ancillary data (e.g. temperature, water vapour, etc.), particle distribution utilizing multi-wavelengths space-borne lidar measurements or balloon size particle and cirrus microphysical-resolved models.

Published
2012
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18. A Raman lidar at La Reunion (20.8° S, 55.5° E) for monitoring water vapor and cirrus distributions in the subtropical upper troposphere: preliminary analyses and description of a future system

Author

Jean-Luc Baray, Jacques Porteneuve, Philippe Keckhut, Béatrice Morel, Holger Vömel, Laurent Robert, Christophe Hoareau, Yann Courcoux, STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de l'Atmosphère et des Cyclones (LACy), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Météo France, Observatoire des Sciences de l'Univers de La Réunion (OSU-Réunion), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Lindenberg Meteorological Observatory - Richard Assmann Observatory (MOL-RAO), Deutscher Wetterdienst [Offenbach] (DWD), Laboratoire d'Energétique, d'Electronique et Procédés (LE2P), Université de La Réunion (UR), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Météo-France, and Energy Lab (ENERGY Lab)

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, lcsh:TA715-787, lcsh:Earthwork. Foundations, [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology, 01 natural sciences, lcsh:Environmental engineering, 010309 optics, Troposphere, Altitude, Lidar, 13. Climate action, Observatory, Diurnal cycle, 0103 physical sciences, Calibration, Environmental science, Cirrus, lcsh:TA170-171, Water vapor, 0105 earth and related environmental sciences, Remote sensing
Abstract

A ground based Rayleigh lidar has provided continuous observations of tropospheric water vapor profiles and cirrus cloud using a preliminary Raman channels setup on an existing Rayleigh lidar above La Reunion over the period 2002–2005. With this instrument, we performed a first measurement campaign of 350 independent water vapor profiles. A statistical study of the distribution of water vapor profiles is presented and some investigations concerning the calibration are discussed. The data set having several long acquisition measurements during nighttime, an analysis of the diurnal cycle of water vapor has also been investigated. Analysis regarding the cirrus clouds is presented and a classification has been performed showing 3 distinct classes. Based on these results, the characteristics and the design of a future lidar system to be implemented at the new Reunion Island altitude observatory (2200 m) for long-term monitoring is presented and numerical simulations of system performance have been realized to compare both instruments.

Published
2012
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19. A preliminary classification of cirrus clouds over Sao Paulo city by systematic lidar observations and comparison with CALIPSO and AERONET data

Author

Eliane G. Larroza, Fábio Lopes, Eduardo Landulfo, and Christophe Hoareau

Subjects
Earth's energy budget, Troposphere, Lidar, Geography, Meteorology, Radiative transfer, Cirrus, Stratosphere, Optical depth, Remote sensing, AERONET
Abstract

Cirrus clouds in the upper troposphere and the lower stratosphere have recently drawn much attention due to their important role and impact on the atmospheric radiative balance. To understand and quantify its impact on earth's atmosphere radiative transfer it is necessary to have information about its optical properties. Such a knowledge is necessary both for comparison with others datasets of cirrus measurements as well as for its influence on radiative transfer models. Cirrus clouds measurements have been performed since 2005 in the Metropolitan Sao Paulo, Brazil (23°33'S, 46o44'W). From MSP-lidar backscatter profiles at 532 nm, and eventually 355 nm, the cloud optical depth (COD) as well as the high of base and top of the clouds are retrieved. A preliminary climatology of cirrus clouds over Sao Paulo using this method has been set. The measurements from Aerosol Robotic Network (AERONET), the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and GOES-10 observations are compared with a ground based lidar dataset for a wide range of cloud types.

Published
2009
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21. Vibrations hydroélastiques de réservoirs élastiques couplés à un fluide interne incompressible à surface libre autour d’un état précontraint

Author

Christophe Hoareau, Laboratoire de Mécanique des Structures et des Systèmes Couplés (LMSSC), Conservatoire National des Arts et Métiers [CNAM] (CNAM), Conservatoire national des arts et metiers - CNAM, and Jean-François Deü

Subjects
Fluid-structure Interaction, Finite element method, Forces suiveuses hydrostatiques, Prestressing, Geometrically non linear, Méthode des éléments-finis, Reduced order model, Modèle d’ordre réduit, Hydroélasticité, Non-Linéarité géométrique, Level-Set, Hydroelasticity, Masse ajoutée, Interaction fluide-Structure, [SPI.MECA.STRU]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of the structures [physics.class-ph], Hydrostatic follower forces, Geometrical non-Linearity, Projection sur base réduite, Ligne de niveau, Added mass, Précontrainte
Abstract

This doctoral thesis focuses on the calculation by the finite element method of the dynamic behavior of prestressed elastic tanks containing an internal liquid with a free surface. We consider that the hydrostatic pressure exerted by the incompressible internal fluid on the flexible walls of the tank causes large displacements, thus leading to a geometric non-linear equilibrium state. The change of stiffness related to this prestressed state induces a shift in the resonance frequencies of the coupled linear vibration problem. The main objective of the work is therefore to estimate, through precise and efficient numerical approaches, the influence of geometric nonlinearities on the hydroelastic behavior of the reservoir/internal liquid system around different equilibrium configurations. The methodology developed is carried out in two stages. The first one consists in calculating the non-linear static state by a total Lagrangian finite element approach.The action of the fluid on the structure is modelled here by hydrostatic following forces. The second step is the calculation of linearized coupled vibrations. In particular, an original reduced order model is proposed to limit the calculation costs associated with the estimation of the added mass effect. Finally, various examples are proposed and compared with results from the literature (from numerical simulations or experimental tests) to show the effectiveness and validity of the different numerical approaches developed in this work.; Cette thèse de doctorat porte sur le calcul par la méthode des éléments finis du comportement dynamique de réservoirs élastiques précontraints contenant un liquide interne à surface libre. Nous considérons que la pression hydrostatique exercée par le fluide interne incompressible sur les parois flexibles du réservoir est à l’origine de grands déplacements, conduisant ainsi à un état d’équilibre non-linéaire géométrique. Le changement de raideur lié à cet état précontraint induit un décalage des fréquences de résonances du problème de vibrations linéaires couplées.L’objectif principal du travail est donc d’estimer, par des approches numériques précises et efficaces, l’influence des non-linéarités géométriques sur le comportement hydroélastique du système réservoir/liquide interne autour de différentes configurations d’équilibre. La méthodologie développée s’effectue en deux étapes. La première consiste à calculer l’état statique non-linéaire par une approche éléments finis lagrangienne totale. L’action du fluide sur la structure est ici modélisée par des forces suiveuses hydrostatiques. La deuxième étape porte sur le calcul des vibrations couplées linéarisées. Un modèle d’ordre réduit original est notamment proposé pour limiter les coûts de calcul associés à l’estimation de l’effet de masse ajoutée. Enfin, divers exemples sont proposés et comparés à des résultats de la littérature (issus de simulations numériques ou d’essais expérimentaux) pour montrer l’efficacité et la validité des différentes approches numériques développées dans ce travail.

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