Éditeur(s) : The Oceanography Society
Résumé : Data assembly and processing centers are essential elements of the operational oceanography infrastructure. They provide data and products needed by modeling and data assimilation systems; they also provide products directly usable for applications. This paper discusses the role and functions of the data centers for operational oceanography. It describes some of the main data assembly centers (Argo and in situ data, altimetry, sea surface temperature) developed during the Global Ocean Data Assimilation Experiment. An overview of other data centers (wind and fluxes, ocean color, sea ice) is also given. Much progress has been achieved over the past 10 years to validate, intercalibrate, and merge altimeter data from multiple satellites. Accuracy and timeliness of products have been improved, and new products have been developed. The same is true for sea surface temperature data through the Global High-Resolution Sea Surface Temperature Pilot Project. A breakthrough in processing, quality control, and assembly for in situ data has also been achieved through the development of the real-time and delayed-mode Argo data system. In situ and remote-sensing data are now systematically and jointly used to calibrate, validate, and monitor over the long term the quality and consistency of the global ocean observing system. Main results are illustrated. There is also a review of the development and use of products that merge in situ and remote-sensing data. Future issues and main prospects are discussed in the conclusion.
Oceanography (1042-8275) (The Oceanography Society), 2009-09 , Vol. 22 , N. 3 , P. 56-69

Droits : 2009 The Oceanography Society
http://archimer.ifremer.fr/doc/2009/publication-6879.pdf
http://archimer.ifremer.fr/doc/00000/6879/

Droits : 2014 Ifremer
http://archimer.ifremer.fr/doc/00180/29100/27514.pdf
http://archimer.ifremer.fr/doc/00180/29100/

Éditeur(s) : Copernicus Gesellschaft Mbh
Résumé : Three methods for automatic detection of mesoscale coherent structures are applied to Sea Level Anomaly (SLA) fields in the South Atlantic. The first method is based on the wavelet packet decomposition of the SLA data, the second on the estimation of the Okubo-Weiss parameter and the third on a geometric criterion using the winding-angle approach. The results provide a comprehensive picture of the mesoscale eddies over the South Atlantic Ocean, emphasizing their main characteristics: amplitude, diameter, duration and propagation velocity. Five areas of particular eddy dynamics were selected: the Brazil Current, the Agulhas eddies propagation corridor, the Agulhas Current retroflexion, the Brazil-Malvinas confluence zone and the northern branch of the Antarctic Circumpolar Current (ACC). For these areas, mean propagation velocities and amplitudes were calculated. Two regions with long duration eddies were observed, corresponding to the propagation of Agulhas and ACC eddies. Through the comparison between the identification methods, their main advantages and shortcomings were detailed. The geometric criterion presents the best performance, mainly in terms of number of detections, duration of the eddies and propagation velocities. The results are particularly good for the Agulhas Rings, which have the longest lifetimes of all South Atlantic eddies.
Ocean Science (1812-0784) (Copernicus Gesellschaft Mbh), 2011 , Vol. 7 , N. 3 , P. 317-334

Droits : Author(s) 2011. This work is distributed under the Creative Commons Attribution 3.0 License. EGU
http://archimer.ifremer.fr/doc/00039/15051/12378.pdf
DOI:10.5194/os-7-317-2011
http://archimer.ifremer.fr/doc/00039/15051/

Éditeur(s) : Amer Meteorological Soc
Résumé : A method to estimate mass and heat transports across hydrographic sections using hydrography together with altimetry data in a geostrophic box inverse model is presented. Absolute surface velocities computed from AVISO altimetry products made up of a combination of sea surface height measurements and geoid estimate are first compared to Ship Acoustic Doppler Current Profiler (S-ADCP) measurements of the Ovide project along hydrographic sections repeated every 2 years in summer from Portugal to Greenland. The rms difference between S-ADCP and altimetry velocities averaged on distances of about a hundred km accounts to 3.3 cm s−1. Considering that the uncertainty of S-ADCP velocities is found at 1.5 cm s−1, altimetry errors are estimated at 3 cm s−1. Transports across Ovide sections previously obtained using S-ADCP data to constrain the geostrophic inverse box model are used as reference. The new method is found useful to estimate absolute transports across the sections, as well as part of their variability. Despite associated uncertainties about 50% larger than when S-ADCP is used, our results for the North Atlantic Current and heat transports, with uncertainties of 10 to 15%, reproduce the variability already observed. The largest uncertainties are found in the estimates of the East Greenland Irminger Current (EGIC) transport (30%), induced by larger uncertainties associated with altimetry data at the western boundary.
Journal Of Atmospheric And Oceanic Technology (0739-0572) (Amer Meteorological Soc), 2011-10 , Vol. 28 , N. 10 , P. 1324-1337

Droits : 2011 American Meteorological Society
http://archimer.ifremer.fr/doc/00038/14921/13751.pdf
DOI:10.1175/2011JTECHO818.1
http://archimer.ifremer.fr/doc/00038/14921/

Observing the Oceans in the 21st Century

Droits : GODAE project office
http://archimer.ifremer.fr/doc/00090/20096/17735.pdf
http://archimer.ifremer.fr/doc/00090/20096/

Éditeur(s) : IEEE
Résumé : Two approaches of ocean color data merging were tested and compared in the North and Equatorial Atlantic Basin: the weighted averaging and the objective analysis. The datasets used were the daily level-3 binned data of chlorophyll-a from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer on the Aqua satellite over the year 2003, which is the first common full year of operation. Since they represent input for both approaches, matchups between the satellite and the in situ data from the SeaWiFS Bio-optical Archive and Storage System and the Atlantic Meridional Transect were first studied to compute a spatial map of the root mean-square error and of the bias. Because of the log distribution of the chlorophyll fields, each approach was applied to untransformed and log-transformed values. The application of the weighted averaging to log-transformed values does not show significant differences in comparison to its application to untransformed values. This is not the case, however, for the objective analysis that gives better results when applied to logtransformed values. Both approaches give combined chlorophyll data of equivalent quality, although the objective analysis could be improved with a better statistical characterization of noise and signal covariance. The main advantage of the objective analysis is its ability to interpolate in space (and time) by taking into account the characteristic scales of chlorophyll-a. As a result, the spatial coverage of the combined data is at least twice as large in the case of objective analysis than weighted averaging. OCR NOT CONTROLLED
IEEE (0196-2892) (IEEE), 2006-11 , Vol. 44 , N. 11 , P. 3436-3451

Droits : 2006 IEEE
http://archimer.ifremer.fr/doc/2006/publication-3631.pdf
DOI:10.1109/TGRS.2006.878441
http://archimer.ifremer.fr/doc/00000/3631/

Éditeur(s) : Amer Geophysical Union
Résumé : The objective of the paper is to analyze the degree of realism of the Parallel Ocean Program ( POP) model of the Los Alamos Laboratory using the combined TOPEX/Poseidon and ERS-1/2 (TPERS) sea level anomaly (SLA) data sets and to present a detailed study of mesoscale characteristics in the North Atlantic. This description spans 8 years of data from 1993 to 2000. At first, we focus on the analysis of the mean eddy kinetic energy ( EKE) and show that the major characteristics of mesoscale variability are realistically simulated despite an overestimation of the EKE model in the Gulf Stream region. We then describe the SLA space and timescales and propagation velocities at a resolution never achieved before. There is a high level of agreement between the model and altimeter values regarding spatial scales and propagation velocities. POP timescales are, however, significantly longer in the subtropical regions. The westward zonal propagation velocity of both the model and the observations are higher than the speed computed from standard Rossby wave theory. The effect of mean current advection on POP and TPERS propagation velocities is also clearly seen in the Labrador Current and in the Gulf Stream and its recirculations. Finally, a study of the seasonal and interannual variability of the high-frequency (HF) EKE is carried out. The model reproduces accurately most of the HF-EKE seasonal variations in the Caribbean Sea and at high latitudes despite a phase advance. A clear HF-EKE interannual variability is then evidenced. Our hypothesis is that a contraction of the subpolar and subtropical gyres due to the North Atlantic Oscillation (NAO) could explain a reduction of the eddy activity in the North Atlantic Current, in the Newfoundland basin, and in the Azores Current. In the Caribbean Sea, the interannual variability of the EKE for both POP and TPERS seems to be caused by an interannual variability of the wind stress.
Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2004-12 , Vol. 109 , N. C1205 , P. 16 PP.

Droits : 2004 AGU
http://archimer.ifremer.fr/doc/00087/19841/17491.pdf
DOI:10.1029/2004JC002360
http://archimer.ifremer.fr/doc/00087/19841/

Éditeur(s) : Amer Geophysical Union
Résumé : This study focuses on the improved estimation of mesoscale surface ocean circulation obtained by merging TOPEX/Poseidon (T/P) and ERS-1 and -2 altimeter measurements between October 1992 and May 1998. Once carefully intercalibrated and homogenized, these data are merged through an advanced global objective analysis method that allows us to correct for residual long wavelength errors and uses realistic correlation scales of ocean dynamics, The high-resolution (0.25 degrees x 0.25 degrees) merged T/P + ERS-1 and -2 sea level anomaly maps provide more homogeneous and reduced mapping errors than either individual data set and more realistic sea level and geostrophic velocity statistics than T/P data alone. Furthermore, the merged T/P + ERS-1 and -2 maps yield eddy kinetic energy (EKE) levels 30% higher than maps of T/P alone. They also permit realistic global estimates of east and north components of EKE and their seasonal variations, to study EKE sources better. A comparison of velocity statistics with World Ocean Circulation Experiment surface drifters in the North Atlantic shows very good agreement. Comparison with contemporary current meter data in various oceanic regimes also produces comparable levels of energy and similar ratios of northward and eastward energy, showing that the maps are suitable to studying anisotropy. The T/P + ERS zonal and meridional components of the mapped currents usually present comparable rms variability, even though the variability in the Atlantic is more isotropic than that in the Pacific, which exhibits strong zonal changes. The EKE map presents a very detailed description, presumably never before achieved at a global scale. Pronounced seasonal changes of the EKE are found in many regions, notably the northeastern Pacific, the northeastern and northwestern Atlantic, the tropical oceans, and the zonally extended bands centered near 20 degrees S in the Indian and western Pacific Oceans and at 20 degrees N in the northwestern nl Pacific.
Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2000-08 , Vol. 105 , N. C8 , P. 19477-19498

Droits : 2000 AGU
http://archimer.ifremer.fr/doc/00079/19033/16617.pdf
DOI:10.1029/2000JC900063
http://archimer.ifremer.fr/doc/00079/19033/

Droits : 2015 Ifremer
http://archimer.ifremer.fr/doc/00254/36504/35050.pdf
http://archimer.ifremer.fr/doc/00254/36504/