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Outline Use of satellite altimetry for oceanography Operational oceanography – GODAE - MERCATOR

From altimetry to operational oceanography, need for a precise geoid. Exemple of the E.U. GOCINA Project. Fabrice Hernandez and P.Y. Le Traon CLS Space Oceanography Division + GOCINA consortium. Outline Use of satellite altimetry for oceanography

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Outline Use of satellite altimetry for oceanography Operational oceanography – GODAE - MERCATOR

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  1. From altimetry to operational oceanography, need for a precise geoid. Exemple of the E.U. GOCINA Project. Fabrice Hernandez and P.Y. Le Traon CLS Space Oceanography Division + GOCINA consortium Outline • Use of satellite altimetry for oceanography • Operational oceanography – GODAE - MERCATOR • Mean dynamic topography (absolute dynamic topography): the present • Conclusions - perspectives for GOCE • The GOCINA project

  2. Absolute dynamic topography from altimetry (1) h =h + G  ’= h ’ One of the main objectives of GOCE is to provide a sufficiently accurate geoid to allow a precise estimation of absolute dynamic topography from altimetry. In practice the best procedure to get an estimation of the absolute dynamic topography (and its error) (h = < h > + h ') from altimetry will be : G h’=h- G • Estimate a mean dynamic topography (< h >) from GOCE , altimetry or other: • difference between MSS and geoid • climatology from in situ data, or synthetic geoid product • ocean model mean • The mean should correspond to a mean over a precise time period determined by the sea level anomaly calculation (typically several years or the duration of an altimetric mission). The longer is the time period, the better as the scales of the mean signal will be larger. • 2. Add this mean dynamic topography to sea level anomaly (h ') derived from repeat-track analysis.

  3. Absolute dynamic topography from altimetry (2) The (main) product that oceanographers will need from GOCE will thus be a mean dynamic topography (and its error) • This product will have a major impact on scientific and operational applications (e.g. GODAE, MERCATOR) of satellite altimetry (e.g. Woodworth et al., 1998; Le Provost et al.,1999) : • better interpretation of altimeter signals (absolute dynamic topography): Sea level monitoring and climate studies… • comparison/combination with in-situ data • general circulation and heat transport • data assimilation and ocean forecasting • ...

  4. Operational oceanographyThe GODAE vision "A global system of observations, communications, modelling and assimilation, that will deliver regular, comprehensive information on the state of the oceans, in a way that will promote and engender wide utility and availability of this resource for maximum benefit to the community” (GODAE Strategic Plan, 2001)

  5. The Global Oceanic Data Assimilation Experiment Objective:To provide a practical demonstration of real-time operationalglobal oceanography • Regular comprehensive description of the ocean circulation at high temporal and spatial resolution • Consistent with a suite of remote and in-situ measurements and appropriate dynamical and physical constraints Includes the main operational and research institutions from Australia, Japan, United States, United Kingdom, France and Norway Main demonstration phase : 2003 to 2005 (prototypes are already running) Climate and seasonal forecasting, marine safety, fisheries, the offshore industry, Navy applications and management of shelf/coastal areas are among the expected beneficiaries of GODAE The integrated description of the ocean that GODAE will provide will also be highly beneficial to the research community

  6. In 2003, the modeling/assimilation unit of the n MERCATOR system is based on two components : Common boundary : 9° N Atlantic • an intermediate resolution North • a high resolution (1/15°) Global Ocean (1/4°) model Atlantic model, including the Mediterranean sea

  7. Forecasts for May 14, 2003 SSH Mixed layer depth 2003: the second MERCATOR Prototype : PSY2

  8. 3000 floats providing T and S profiles (0-2000 m) every 10 days and measuring velocity at 2000 m = • vertical description • large scale and seasonal variations • water masses • improved estimation of absolute mean dynamic topography (a few cm rms) • …

  9. SSALTO/DUACS (CLS/CNES) : Real time processing of TOPEX/POSEIDON, ERS-1/2, GFO, Jason-1 and ENVISAT Mesoscale to climate, surface integrated circulation Serving operational oceanography (GODAE) and climate forecasting centers Real time processing (2-3 days) Global crossover minimizations, inverse techniques to remove long wavelength errors => high accuracy SSH (Sea Surface Height) data Consistent mean profiles to reference multiple altimeter data => consistent SLA (Sea Level Anomaly) data Products directly useable for scientific and operational applications (climate and mesoscale) Real time processing of T/P and ERS-2 data during the 1998 El Nino

  10. Need for operational oceanography: Maps of SLA can be produced with a good accuracy (better than 5cm and 10 cm/s) and describe scales shorter than 100 km and 5 days. The (main) product that oceanographers will need from GOCE will thus be a mean dynamic topography (and its error) at equivalent scale and accuracy ! SSALTO/DUACS : High resolution from T/P, ERS-2 and GFO data + synthetic mean dynamic topography

  11. Mean Dynamic Topography from POCM, Levitus and EGM96-MSS rms differences are about 12 cm (wavelengths > 2000 km) EGM96 - MSS Levitus (700 m) POCM

  12. m m MSS CLS01 – EIGEN2 Levitus (700 m) OCCAM

  13. Mean Dynamic Topography (conclusion…) • Improvements needed in both accuracy and resolution… • Based on CHAMP, GRACE, GOCE (large and medium scales), in-situ data and models (shortest scales, and consistent physics) • Homogeneous period • ...

  14. Need for operational oceanography: Impact of GOCE and high accuracy MDT Improvement in the 7-day sea level anomaly forecast due to the use of a “GCE” MDT (Dombrowsky, 1999). Units from 0 to 50 cm2 Use of a “GOCE” MDT allow a better prediction of the eddy field, by about 15% of the signal variance for a 7-day prediction. 2-week forecast error with “GOCE” MDT is equivalent to 1-week forecast error with “today” MDT This improvement will come in addition to the improvement in the knowledge of the mean circulation itself. The effect should be larger for longer term forecast

  15. Impact of the Synthetic MDT (Rio, 2003) in MERCATOR Synthetic MDT MERCATOR MDT Difference • More realistic (comparison to drifter, hydrographic observations) • Enhance the forecasting capability of the system?

  16. Impact of the Synthetic MDT (Rio, 2003) in MERCATOR 6 months of the impact experiment (operational configuration … Sept 01 to April 02) MKE comparison (cm2/s2): stronger mean currents. Subpolar gyre better defined

  17. Impact of the Synthetic MDT (Rio, 2003) in MERCATOR 6 months of the impact experiment (operational configuration … Sept 01 to April 02) EKE comparison (cm2/s2): intensification of the model mesoscale variability

  18. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic GOCINA will develop generic tools to enhance ocean analysis using Earth observation data from ENVISAT and GOCE. The project will examine the mass and heat exchange across the Greenland-Scotland Ridge. This analysis will give invaluable information on the ocean role in climate. The project will in particular support the GOCE mission with a set of specific recommendation for integrating GOCE in ocean circulation studies and an accurate geoid model for validation purposes. A major task is to determine an accurate geoid in the region between Greenland and the UK and, thereby, create a platform for validation of future GOCE Level 2 data and higher order scientific products. The new and accurate geoid is used together with an accurate mean sea surface to determine the mean dynamic topography. The mean dynamic topography is used for improved analysis of the ocean circulation and transport through the straits between Greenland and the UK. Gocina: 36 mois (11/2002 - 11/2005)

  19. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic Partner 1 (KMS):Kort & MatrikelstyrelsenGeodetic Department, DK-2400 København Att: Per Knudsen (coordinator)Partner 2 (NMA):Norwegian Mapping AuthorityGeodetic Institute, N-3504 HønefossAtt: Dag SolheimPartner 3 (UEDIN):The University of EdinburghGeography and Geophysics, EH9 3JW EdinburghAtt: Roger HipkinPartner 4 (UREADES):University of ReadingEnvironmental Systems Science Centre, RG6 6AL ReadingAtt: Keith HainesPartner 5 (NERSC):Nansen Environmental andRemote Sensing CenterN-5059 BergenAtt: Johnny JohannessenPartner 6 (CLS):Collecte Localisation SatellitesSpace Oceanography Division,F-31526 Ramonville St. AgneAtt: Fabrice Hernandez The partners each have a high international reputation for expertise relevant to their specific roles. KMS, NMA, and UEDIN have expertise in geodetic disciplines associated with geoid determination. UREADES, NERSC, and CLS have expertise in oceanographic disciplines associated with ocean circulation and data assimilation. KMS and CLS have expertise in processing satellite altimetry for both geodetic and oceanographic purposes. Strong collaboration with OCTAS (Norway) http://www.octas.statkart.no/

  20. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic • WP1: Geoid determination (R. Forsberg/R. Hipkin) • Collect marine gravity data • Complete with air-borne gravity survey + intercalibration • Compute gravimetric geoid + errors using state-of-the-art method (marine, land, topo, airborne data) with the mgal precision • Take into account available CHAMP & GRACE data to enhance long wavelength • .

  21. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic

  22. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic

  23. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic

  24. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic Airborne gravimetry (collaboration with OCTAS)

  25. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic • WP2: Mean Sea Surface Determination (O. Andersen/F. Hernandez) • Compile satellite altimetry: T/P, Jason-1, ERS-1/2, EnviSat, Geosat, GFO up to 2002 • Analyse existing MSS in the area (KMS01, CLS01, GSFC00.1) • Determine a high resolution MSS (1/60°) • .

  26. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic

  27. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic • WP3: Mean dynamic topography determination (K. Haines/F.Hernandez) • Collect existing MDT (climatology, model, etc…) and evaluation • Compile in-situ data (hydrographic data, surface drifters etc…) • Determine a MDT from climatology • Determine a synthetic MDT • Determine a model MDT from OGCM .

  28. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic

  29. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic • WP4: Assessment and Validation (D. Solheim/A. Vest) • To assess the initial models residuals • Compare the different MDT to in-situ data • Infer error characteristics of the different models • .

  30. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic

  31. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic MDT = KMS-01 MSS - ”Tallinn” geoid OCCAM MDT = KMS-01 MSS – EGM96 geoid MDT = KMS-01 MSS – geoid36.eig

  32. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic MDT = KMS-01 MSS - ”Tallinn” geoid OCCAM MDT = KMS-01 MSS – EGM96 geoid MDT = KMS-01 MSS – geoid36.eig

  33. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic • WP5: Technique integration (R. Hipkin) • Integrate the three quantities (MSS, MDT, geoid) and errors • Testing new techniques (data assimilation and geoid inversion) for calculating the best possible local solution • Investigate impact of the GOCE errors • WP6: Ocean circulation and transport (F. Hernandez/J. Johannessen) • Testing the MDT in OGCMs (impact in mass and heat transport across the straits, outflow…) • Testing the predictability at seasonal/interannual scales (NAO prediction) • WP7: Recommendations for integrating GOCE (J. Johannessen) • Educate and prepare the community in using GOCE data for oceanography including sea level and climate research as well as operational prediction • Develop methods for generating regional gravity fields and use them to generate a best possible regional gravity field and geoid model for the North Atlantic that can be used in validation of the GOCE products • .

  34. The GOCINA project (5th E.U. FP)http://www.gocina.dk/Geoid and Ocean Circulation in the North Atlantic • … If GOCE is launched in 2006, the GOCINA would be finished, but conclusions could be applied • GOCINA is a unique community (geodesy and oceanography) for calibration and validation • Direct outcome and applications for several communities (climate prediction, ocean studies, operational oceanography, marine security and oil industry…)

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