International financial flows in the new normal: Key patterns (and why we should care)

This paper documents recent trends in international financial flows, based on a newly assembled dataset covering 40 advanced and emerging countries. It highlights four stylized facts: first, the "Great Retrenchment" that took place during the crisis has proved very persistent; second, this fall can predominantly be related to advanced economies, especially in Western Europe; third, net flows have fallen substantially relative to the years preceding the crisis; and fourth, profound changes have occurred in the composition of international financial flows in ways which should help to strengthen resilience and deliver genuine cross-border risk-sharing. This paper then turns to possible explanations for and likely implications of these changes, with regard to international financial stability issues

Analysis of Reinforced Concrete Buildings Using Multipath Lidar

International audienceThis paper compares the modal analysis of reinforced-concrete buildings obtained using sensitive velocimeters and coherent LIDAR. Ambient vibrations are recorded by these two systems and processing using operative modal analysis method for getting building frequency and mode shapes. Real-scale trials applied to five buildings located at Grenoble (France) are presented. The efficiency and reliability of the Lidar is discussed and the modal parameters measured by Lidar at a range of 200m and by in-situ velocimeters are compared. The results are in good agreement and allow us to conclude on the ability of the coherent Lidar to assess modal parameters of existing buildings at long range and without any retroreflectors placed on the structures. The results open new perspectives for remotely testing buildings, without getting inside, facilitating dynamic analysis of buildings for earthquake engineering applications

Measures de vent 3D avec le lidar Doppler coherent Live à bord d'un avion

International audienceA three-dimensional (3D) wind profiling Lidar, based on the latest high power 1.5 µm fiber laser development at Onera, has been successfully flown on-board a SAFIRE (Service des Avions Français Instrumentés pour la Recherche en Environnement) ATR42 aircraft. The Lidar called LIVE (LIdar VEnt) is designed to measure wind profiles from the aircraft down to ground level, with a horizontal resolution of 3 km, a vertical resolution of 100 m and a designed accuracy on each three wind vector components better than 0.5 m.s −1. To achieve the required performance, LIVE Lidar emits 410 µJ laser pulses repeating at 14 KHz with a duration of 700 ns and uses a conical scanner of 30 • total opening angle and a full scan time of 17 s.Un lidar vent 3D, basé sur le dernier développement de laser à fibre de 1,5 µm à haute puissance de l’ONERA a été testé avec succès à bord d’un avion SAFIRE ATR42. Le lidar appelé LIVE est conçu pour mesurer les profils de vent de l’avion jusqu'au sol, avec une résolution horizontale de 3 km, une résolution verticale de 100 m et une précision calculée supérieure à 0,5 m / s pour chaque composante du vecteur du vent

Highly variable upper and abyssal overturning cells in the South Atlantic

The Meridional Overturning Circulation (MOC) is a primary mechanism driving oceanic heat redistribution on Earth, thereby affecting Earth’s climate and weather. However, the full-depth structure and variability of the MOC are still poorly understood, particularly in the South Atlantic. This study presents unique multiyear records of the oceanic volume transport of both the upper (~3100 meters) overturning cells based on daily moored measurements in the South Atlantic at 34.5°S. The vertical structure of the time-mean flows is consistent with the limited historical observations. Both the upper and abyssal cells exhibit a high degree of variability relative to the temporal means at time scales, ranging from a few days to a few weeks. Observed variations in the abyssal flow appear to be largely independent of the flow in the overlying upper cell. No meaningful trends are detected in either cell.Fil: Kersalé, Marion. National Ocean And Atmospheric Administration; Estados Unidos. University of Miami; Estados UnidosFil: Meinen, Christopher S.. National Ocean And Atmospheric Administration; Estados UnidosFil: Perez, Renellys C.. National Ocean And Atmospheric Administration; Estados UnidosFil: Le Hénaff, Matthieu. National Ocean And Atmospheric Administration; Estados Unidos. University of Miami; Estados UnidosFil: Valla, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: Lamont, Tarron. University of Cape Town; SudáfricaFil: Sato, Olga T.. Universidade de Sao Paulo; BrasilFil: Dong, Shenfu. National Ocean And Atmospheric Administration; Estados UnidosFil: Terre, T.. University of Brest; Francia. Centre National de la Recherche Scientifique; FranciaFil: van Caspel, M.. Universidade de Sao Paulo; BrasilFil: Chidichimo, María Paz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: van den Berg, Marcel Alexander. Department of Environmental Affairs; SudáfricaFil: Speich, Sabrina. University Of Cape Town; SudáfricaFil: Piola, Alberto Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ecole Normale Superieure. Laboratoire de Meteorologie Dynamique; Francia. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; Argentina. Universidad de Buenos Aires; ArgentinaFil: Campos, Edmo. Universidade de Sao Paulo; Brasil. American University Of Sharjah.; Emiratos Árabes UnidosFil: Ansorge, Isabelle. University of Cape Town; SudáfricaFil: Volkov, Denis L.. University of Miami; Estados Unidos. National Ocean And Atmospheric Administration; Estados UnidosFil: Lumpkin, Rick. National Ocean And Atmospheric Administration; Estados UnidosFil: Garzoli, S. L.. University of Miami; Estados Unidos. National Ocean And Atmospheric Administration; Estados Unido

Aeronautics lidar revisited - Towards lidar-based gust and turbulence measurement for aircraft load alleviation control

We give an overview of the authors' and their institutions' latest R&D activities regarding Direct-Detection Doppler-Wind-Lidar (DD-DWL) for the usage as remote flow sensor on civil aircraft. The purpose of such a lidar, when flying through Clear Air Turbulence (CAT) at cruise altitudes, is delivering sufficient turbulent wind information for feeding a chain of gust reconstruction, control and command modules. Hence, aerodynamic effects on the aircraft structure shall be mitigated. The long-standing record of the ONERA and DLR lidar groups in aeronautics' application lidar allowed us recently to team up in the European Clean Aviation Joint Undertaking (CAJU) co-financed project UP Wing with the agenda of maturing the critical technologies (like laser, Doppler spectrometric receiver, etc.) and validating these at component and system level with extensive ground and also airborne tests. Here, we present the main bricks of this technology suite, an overview of some prior and actual achievements and some perspective

Etude d'un lidar doppler impulsionnel à laser Erbium fibré pour des mesures de champ de vent dans la couche limite de l'atmosphère

Un travail de thèse a été entrepris pour la réalisation d'un anémomètre laser cohérent impulsionnel pour la mesure de champ de vent résolue en distance dans la basse atmosphère. Lors de sa propagation, l'impulsion permet de sonder graduellement l'atmosphère dans le sens ascendant. Il est ainsi possible de résoudre en distance la mesure de vitesse en découpant l'analyse du signal rétrodiffusé en multiples fenêtres temporelles. L'originalité de ce travail de thèse est l'utilisation d'une source laser fibrée 1,55 m en régime impulsionnel nanoseconde. La technologie Erbium fibrée permet la réalisation d'instruments fiables, compacts et à sécurité oculaire. Un simulateur de performance instrumentale permet de calculer le rapport porteuse sur bruit d'un lidar mono ou bistatique, utilisant des configurations de faisceaux gaussiens tronqués avec ou sans turbulence atmosphérique. Pour la turbulence, le simulateur utilise un code de propagation par écran de phase. Le calcul exact de la borne de Cramér-Rao permet de dimensionner les performances du traitement numérique associé à l'instrument. Cette partie comporte un travail de modélisation fine du spectre du signal lidar qui met en évidence une forme de " spectral leakage " lié à la décorrélation du signal due à la nature impulsionnelle de l'instrument. La disponibilité d'une source de 20 J a permis la réalisation d'un prototype permettant la mesure simultanée de trois cases distances jusqu'à 130 mètres de distance et de valider par l'expérience le travail de modélisation entrepris au cours de cette thèse.A PhD work has been undertaken for the realization of an impulse coherent laser anemometer for the measurement of wind field solved in distance in the lower atmosphere. During its propagation, the pulse gradually probe the atmosphere in the ascending direction. It is thus possible to realize a distance resolved velocity measurement by cutting out the analysis of the signal retrodiffused in multiple temporal windows. The originality of this PhD work is the use of a 1.55 m erbium fiber amplifier in a nanosecond pulsed mode, which allows the realization of compact and reliable instruments, with ocular safety. The instrumental simulator calculates the carrier to noise ratio of a mono or bistatic lidar, using configurations of truncated Gaussian beams with or without atmospheric turbulence. In order to account for atmospheric turbulence, the simulator uses a screen phase propagation code.The exact calculation of the Cramér-Rao lower bound allows us to predict the performances of the digital processing associated with the instrument. This part contains a fine model of the spectrum of the lidar signal which highlights a form of "spectral leakage" related to the decorrelation of the signal due to the pulsed nature of the instrument. he availability of a laser able of 20 J pulses allowed the realization of a prototype which was able to make three simultaneous measurements at distances up to 130 meters, thus giving us the opportunity to validate by the experiment the spectrum model undertaken during this PhD work.PARIS-Télécom ParisTech (751132302) / SudocSudocFranceF

Simulation of Doppler Lidar Measurement Range and Data Availability

International audienceThe measurement range of a coherent wind Doppler lidar (CWDL) along a laser beam is the maximum distance from the lidar where wind speed data are accurately retrieved. It means that, at this distance, a sufficient number of emitted laser photons are backscattered and received by the lidar. Understanding of the propagation of the laser through the atmosphere, and particularly the backscattering and extinction processes from aerosols, is therefore important to estimate the metrological performances of a CWDL instrument. The range is directly related to specific instrument characteristics and atmospheric content, such as the aerosols type, size, and density distributions. Associated with the measurement range is the notion of data availability, which can be defined, at a given range and over a time period, as the percentage number of data retrieved correctly by the CWDL over the total number of measurement attempts.This paper proposes a new approach to predict the CWDL data availability and range of measurement using both instrumental simulation and atmospheric observations of aerosol optical properties from weather stations and simulations. This method is applied in several CWDL measurement campaigns during which estimated data availabilities and ranges are compared with the observations. It is shown that it is fairly possible to anticipate the data availability and the range coverage of CWDL technology at any site of interest where atmospheric data are available. The method also offers an additional way to diagnose the operation of the instrument and will help in the design of future instruments