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| Registros recuperados: 19 | |
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| Hoteit, I; Pham, Dt; Blum, J. |
| A new data assimilation scheme derived from the singular evolutive extended Kalman (Seek) filter is introduced. The novel feature of the new filter is its correction basis which is partially local in the sense that it consists of "global" and "local" vectors, the later obtained from a local empirical orthogonal functions (Eof) analysis. Such an analysis was introduced in order to better represent the local variability of the ocean. This not only significantly reduces the implementation cost but may also improve the representativeness of the correction basis of the filter. The performance of this scheme is evaluated through twin experiments conducted in a realistic setting of the OPA model over the tropical Pacific zone. The results are compared against... |
| Tipo: Text |
Palavras-chave: Filtre Seek; Analyse Eof; Facteur oublié; Data assimilation; Seek filter; Eof analysis; Forgetting factor. |
| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/00321/43244/42973.pdf |
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| Ferron, Bruno. |
| The increasing number of oceanic observations calls for the use of synthetic methods to provide consistent analyses of the oceanic variability that will support a better understanding of the underlying mechanisms. In this study, a 1/3 degrees eddy-permitting model of the North Atlantic (from 20 degrees S to 70 degrees N) is combined with a 4D-variational method to estimate the oceanic state from altimeter observations. This resolution allows a better extraction of the physical content of altimeter data since the model spatial scales are more consistent with the data than coarser assimilation exercises because of a lower error in model representativity. Several strategies for the assimilation window are tested through twin experiments carried out under the... |
| Tipo: Text |
Palavras-chave: Ocean modelling; Data assimilation; Variational method; Meso-scale; Sea surface height; Heat transport; Meridional overturning. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00044/15534/12956.pdf |
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| Forget, Gael; Ferron, Bruno; Mercier, Herle. |
| Argo is a global array of profiling floats that provides temperature (T) and salinity (S) profiles from 2000 m to the surface every ten days with a nominal spatial resolution of 3 degrees. Here we present idealized experiments where the adjoint method is used to synthesize simulated sets of Argo profiles with a general circulation model, over a one-year period, in the North Atlantic. Using a number of drifting profilers consistent with Argo deployment objectives, the simulated array permits one to identify large-scale anomalies in the hydrography and circulation, despite the presence of a simulated eddy noise of large amplitude. Model dynamics provide an objective means to distinguish eddy noise from large-scale oceanic variability, and to infer the... |
| Tipo: Text |
Palavras-chave: General circulation model; Argo; Twin experiment; 4DVAR; Data assimilation. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-3721.pdf |
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| Rubio, Anna; Mader, Julien; Corgnati, Lorenzo; Mantovani, Carlo; Griffa, Annalisa; Novellino, Antonio; Quentin, Céline; Wyatt, Lucy; Schulz-stellenfleth, Johannes; Horstmann, Jochen; Lorente, Pablo; Zambianchi, Enrico; Hartnett, Michael; Fernandes, Carlos; Zervakis, Vassilis; Gorringe, Patrick; Melet, Angélique; Puillat, Ingrid. |
| High Frequency Radar (HFR) is a land-based remote sensing instrument offering a unique insight to coastal ocean variability, by providing synoptic, high frequency and high resolution data at the ocean atmosphere interface. HFRs have become invaluable tools in the field of operational oceanography for measuring surface currents, waves and winds, with direct applications in different sectors and an unprecedented potential for the integrated management of the coastal zone. In Europe, the number of HFR networks has been showing a significant growth over the past 10 years, with over 50 HFRs currently deployed and a number in the planning stage. There is also a growing literature concerning the use of this technology in research and operational oceanography. A... |
| Tipo: Text |
Palavras-chave: High frequency radar; Operational oceanography; Coastal observing systems; Radar remote sensing; Surface currents; Surface waves; Model assessment; Data assimilation. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00368/47879/47895.pdf |
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| Ciavatta, S.; Kay, S.; Saux-picart, S.; Butenschon, M.; Allen, J. I.. |
| This paper presents the first decadal reanalysis simulation of the biogeochemistry of the North West European shelf, along with a full evaluation of its skill, confidence, and value. An error-characterized satellite product for chlorophyll was assimilated into a physical-biogeochemical model of the North East Atlantic, applying a localized Ensemble Kalman filter. The results showed that the reanalysis improved the model simulation of assimilated chlorophyll in 60% of the study region. Model validation metrics showed that the reanalysis had skill in matching a large data set of in situ observations for 10 ecosystem variables. Spearman rank correlations were significant and higher than 0.7 for physical-chemical variables (temperature, salinity, and oxygen),... |
| Tipo: Text |
Palavras-chave: Marine ecosystems; Data assimilation; Ocean color; Air-sea flux of carbon dioxide; Dissolved oxygen; Marine policy. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00383/49422/49850.pdf |
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| Le Traon, Pierre-yves; Reppucci, Antonio; Alvarez Fanjul, Enrique; Aouf, Lotfi; Behrens, Arno; Belmonte, Maria; Bentamy, Abderrahim; Bertino, Laurent; Brando, Vittorio Ernesto; Kreiner, Matilde Brandt; Benkiran, Mounir; Carval, Thierry; Ciliberti, Stefania A.; Claustre, Hervé; Clementi, Emanuela; Coppini, Giovanni; Cossarini, Gianpiero; De Alfonso Alonso-muñoyerro, Marta; Delamarche, Anne; Dibarboure, Gerald; Dinessen, Frode; Drevillon, Marie; Drillet, Yann; Faugere, Yannice; Fernández, Vicente; Fleming, Andrew; Garcia-hermosa, M. Isabel; Sotillo, Marcos García; Garric, Gilles; Gasparin, Florent; Giordan, Cedric; Gehlen, Marion; Gregoire, Marilaure L.; Guinehut, Stephanie; Hamon, Michel; Harris, Chris; Hernandez, Fabrice; Hinkler, Jørgen B.; Hoyer, Jacob; Karvonen, Juha; Kay, Susan; King, Robert; Lavergne, Thomas; Lemieux-dudon, Benedicte; Lima, Leonardo; Mao, Chongyuan; Martin, Matthew J; Masina, Simona; Melet, Angelique; Buongiorno Nardelli, Bruno; Nolan, Glenn; Pascual, Ananda; Pistoia, Jenny; Palazov, Atanas; Piolle, Jean-francois; Pujol, Marie Isabelle; Pequignet, Anne Christine; Peneva, Elisaveta; Pérez Gómez, Begoña; Petit De La Villeon, Loic; Pinardi, Nadia; Pisano, Andrea; Pouliquen, Sylvie; Reid, Rebecca; Remy, Elisabeth; Santoleri, Rosalia; Siddorn, John; She, Jun; Staneva, Joanna; Stoffelen, Ad; Tonani, Marina; Vandenbulcke, Luc; Von Schuckmann, Karina; Volpe, Gianluca; Wettre, Cecilie; Zacharioudaki, Anna. |
| The Copernicus Marine Environment Monitoring Service (CMEMS) provides regular and systematic reference information on the physical and biogeochemical ocean and sea-ice state for the global ocean and the European regional seas. CMEMS serves a wide range of users (more than 15,000 users are now registered to the service) and applications. Observations are a fundamental pillar of the CMEMS value-added chain that goes from observation to information and users. Observations are used by CMEMS Thematic Assembly Centres (TACs) to derive high-level data products and by CMEMS Monitoring and Forecasting Centres (MFCs) to validate and constrain their global and regional ocean analysis and forecasting systems. This paper presents an overview of CMEMS, its evolution,... |
| Tipo: Text |
Palavras-chave: Ocean; Observing systems; Satellite; In situ; Data assimilation; Services. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00498/60983/64389.pdf |
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| Duong, Quoc-phi; Langlade, Sébastien; Payan, Christophe; Husson, Romain; Mouche, Alexis; Malardel, Sylvie. |
| Tropical cyclone (TC) monitoring and forecast in the South West Indian Ocean (SWIO) basin remain challenging, notably because of the lack of direct observations. During the 2018–2019 cyclone season, S-1 Sentinel SAR images were acquired, as part of the ReNovRisk-Cyclone research program, giving access to unprecedented detailed TC wind structure description without wind speed limitation. This paper assesses the quality of these data and the impact of their assimilation for TC forecasts. SAR observations are compared with analyses from a convection-permitting, limited area model AROME OI 3D-Var and with wind products used for operational TC monitoring. Their bias depends on the angle of incidence of the radar and the observation error is larger for extreme... |
| Tipo: Text |
Palavras-chave: SAR; 3D-Var; Data assimilation; Tropical cyclone; Sentinel; IDAI; GELENA. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00692/80373/83490.pdf |
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| Cotton, J.; Francis, P.; Heming, J.; Forsythe, M.; Reul, Nicolas; Donlon, C.. |
| A new generation of L-band sensors, such as ESA's Soil Moisture Ocean Salinity (SMOS) mission, have the capability to provide information on the ocean-surface wind speed under high wind and rain conditions. In this study we evaluate the use of SMOS wind speeds within Met Office numerical weather prediction (NWP). Observation minus model background (O-B) departure statistics are used to investigate SMOS error characteristics, quality flags, and develop a quality control method. Observation errors and spatial correlation distances are estimated using a statistical method. Observing system experiments are performed to diagnose the impact of SMOS on NWP forecasts and analyses, including tropical cyclone (TC) predictions. The quality of SMOS retrievals appears... |
| Tipo: Text |
Palavras-chave: SMOS; L-band wind speed; Data assimilation; Tropical cyclones; NWP. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00417/52868/53782.pdf |
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| Fablet, Ronan; Viet, P.; Lguensat, R.; Chapron, Bertrand. |
| We address in this paper the reconstruction of irregurlarlysampled image time series with an emphasis on geophysical remote sensing data. We develop a data-driven approach, referred to as an analog assimilation and stated as an ensemble Kalman method. Contrary to model-driven assimilation models, we do not exploit a physically-derived dynamic prior but we build a data-driven dynamic prior from a representative dataset of the considered image dynamics. Our contribution is here to extend analog assimilation to images, which involve high-dimensional state space.We combine patch-based representations to a multiscale PCA-constrained decomposition. Numerical experiments for the interpolation of missing data in satellite-derived ocean remote sensing images... |
| Tipo: Text |
Palavras-chave: Data assimilation; Irregular sampling; Image time series; Data-driven methods; Kalman methods. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00403/51440/52009.pdf |
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| Carroll, D.; Menemenlis, D.; Adkins, J. F.; Bowman, K. W.; Brix, H.; Dutkiewicz, S.; Fenty, I.; Gierach, M. M.; Hill, C.; Jahn, O.; Landschutzer, P.; Lauderdale, J. M.; Liu, J.; Manizza, M.; Naviaux, J. D.; Roedenbeck, C.; Schimel, D. S.; Van Der Stocken, T.; Zhang, H.. |
| Quantifying variability in the ocean carbon sink remains problematic due to sparse observations and spatiotemporal variability in surface ocean pCO(2). To address this challenge, we have updated and improved ECCO-Darwin, a global ocean biogeochemistry model that assimilates both physical and biogeochemical observations. The model consists of an adjoint-based ocean circulation estimate from the Estimating the Circulation and Climate of the Ocean (ECCO) consortium and an ecosystem model developed by the Massachusetts Institute of Technology Darwin Project. In addition to the data-constrained ECCO physics, a Green's function approach is used to optimize the biogeochemistry by adjusting initial conditions and six biogeochemical parameters. Over seasonal to... |
| Tipo: Text |
Palavras-chave: Ocean modeling; Biogeochemistry; Ocean carbon cycle; Data assimilation; Air‐ Sea CO2 flux; Ecosystem model. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00676/78824/81108.pdf |
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| Forget, Gael; Mercier, Herle; Ferron, Bruno. |
| A set of Argo profiles collected in the North Atlantic between May 2002 and April 2003 is combined with a low-resolution general circulation model (GCM) using the adjoint method. Fitting the real hydrographic observations leads to vast improvements in the model circulation., including the sea surface height and the meridional heat transport. We find striking differences in basin-scale transports compared with previous assimilation experiments that use the same GCM and a similar spatial resolution. Based on forward modeling studies, it is argued that these differences are due to different assimilation experiment durations. Over 1 year, the hydrography interpolated with the GCM from Argo profiles better represents the contemporary structures than does a... |
| Tipo: Text |
Palavras-chave: General circulation model; Argo; In situ observations; 4DVAR; Data assimilation. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-3920.pdf |
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| Mairesse, Aurélien. |
| The study of past climates and of mechanisms that have influenced their evolution is the key to anticipate the future climate changes. This doctoral thesis focusses on the Holocene climate, the ongoing interglacial, that starts about 11,700 years ago. The current paleoclimate knowledge is based on the one hand, on the climate models results and, on the other hand, on the reconstruction of physical variables derived from climate archives as the ice cores, the marine cores or the pollens for instance. These two types of information are complementary. Here we have combined them to obtain reconstructions of past climates using data assimilation. This technique is standard in many disciplines but not yet in paleoclimatology. The data assimilation method applied... |
| Tipo: Text |
Palavras-chave: Climate; Data assimilation; Paleoclimate; Holocene; LOVECLIM model; Proxy record. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00506/61719/65687.pdf |
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| Registros recuperados: 19 | |
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