During the Global Ocean Data Assimilation Experiment (GODAE), seven international operational centers participated in a dedicated modeling system intercomparison exercise from February to April 2008. The objectives were: (1) to show GODAE global-ocean and basin-scale forecasting systems of different countries in routine interaction and continuous operation, (2) to assess the quality and perform scientific validation of the ocean analyses and the forecasting performance of each system, and (3) to learn from this exercise in order to increase interoperability and collaboration in real time. The validation methodology has steadily improved through several validation experiments and projects performed within the operational oceanography community. It relies on common approaches and standardization of outputs, with a set of diagnostics based on fully detailed metrics that characterize its strengths and weaknesses, but it also provides error levels for ocean estimates. The ocean forecasting systems provide daily fields of mesoscale water mass distribution and ocean circulation, with an option for sea-ice variations. We present a subset of the intercomparisons performed over different areas, showing general ocean circulation in agreement with known patterns. We also present some accuracy assessments through comparison with observed data.

Hernandez, F., L. Bertino, G. Brassington, E. Chassignet, J. Cummings, F. Davidson, M. Drévillon, G. Garric, M. Kamachi, J.-M. Lellouche, R. Mahdon, M.J. Martin, A. Ratsimandresy, and C. Regnier. 2009.  Validation and intercomparison studies within GODAE. Oceanography 22(3):128–143, https://doi.org/10.5670/oceanog.2009.71.

Bell, M.J., M. Lefèbvre, P.-Y. Le Traon, N. Smith, and K. Wilmer-Becker. 2009. The Global Ocean Data Assimilation Experiment (GODAE). Oceanography 22(3):14–21.

Blower, J.D., F. Blanc, M. Clancy, P. Cornillon, C. Donlon, P. Hacker, K. Haines, S.C. Hankin, T. Loubrieu, S. Pouliquen, and others. 2009. Serving GODAE data and products to the ocean community. Oceanography 22(3):70–79.

Brasseur, P. 2006. Ocean data assimilation using sequential methods based on Kalman filter. Pp. 371–316 in GODAE Summer School in “Ocean Weather Forecasting: An Integrated View of Oceanography.” E.P. Chassignet and J. Verron, eds, Springer, Lallonde les Maures, France.

Clark, C., and the In Situ Observing System Authors, and S. Wilson and the Satellite Observing System Authors. 2009. An overview of global observing systems relevant to GODAE. Oceanography 22(3):22–33.

Crosnier, L., and C. Le Provost. 2007. Inter-comparing five forecast operational systems in the North Atlantic and Mediterranean basins: The MERSEA-strand1 methodology. Journal of Marine Systems 65:354–375.

Crosnier, L., C. Le Provost, and MERSEA Strand1 Team. 2006. Internal metrics definition for operational forecast systems inter-comparison: Examples in the North Atlantic and Mediterranean Sea. Pp. 455–465 in GODAE Summer School in “Ocean Weather Forecasting: An Integrated View of Oceanography.” E.P. Chassignet and J. Verron, eds, Springer, Lallonde les Maures, France.

Cummings, J., L. Bertino, P. Brasseur, I. Fukumori, M. Kamachi, M.J. Martin, K. Mogensen, P. Oke, C.E. Testut, J. Verron, and A. Weaver. 2009. Ocean data assimilation systems for GODAE. Oceanography 22(3):96–109.

De Mey, P., P. Craig, F. Davidson, C.A. Edwards, Y. Ishikawa, J.C. Kindle, R. Proctor, K.R. Thompson, J. Zhu, and the GODAE Coastal and Shelf Seas Working Group (CSSWG) community. 2009. Applications in coastal modeling and forecasting. Oceanography 22(3):198–205.

Dombrowsky, E., L. Bertino, G.B. Brassington, E.P. Chassignet, F. Davidson, H.E. Hurlburt, M. Kamachi, T. Lee, M.J. Martin, S. Mei, and M. Tonani. 2009. GODAE systems in operation. Oceanography 22(3):80–95.

Donlon, C.J., K.S. Casey, I.S. Robinson, C.L. Gentemann, R.W. Reynolds, I. Barton, O. Arino, J. Stark, N. Rayner, P. LeBorgne, and others. 2009. The GODAE High-Resolution Sea Surface Temperature Pilot Project. Oceanography 22(3):34–45.

Hurlburt, H.E., G.B. Brassington, Y. Drillet, M. Kamachi, M. Benkiran, R. Bourdallé-Badie, E.P. Chassignet, G.A. Jacobs, O. Le Galloudec, J.-M. Lellouche, and others. 2009. High-resolution global and basin-scale ocean analyses and forecasts. Oceanography 22(3):110–127.

Johnson, E.S., F. Bonjean, G.S.E. Lagerloef, J.T. Gunn, and G.T. Mitchum. 2007. Validation and error analysis of OSCAR sea surface currents. Journal of Atmospheric and Oceanic Technology 24:688–701.

Larnicol, G., S. Guinehut, M.-H. Rio, M. Drévillon, Y. Faugère, and G. Nicolas. 2006. The global observed ocean products of the French Mercator project. International Symposium on Radar Altimetry: 15 Years of Altimetry, ESA/CNES.

Locarnini, R.A., A.V. Mishonov, J.I. Antonov, T.P. Boyer, and H.E. Garcia. 2006. World Ocean Atlas 2005, Volume 1: Temperature. S. Levitus, ed., NOAA Atlas NESDIS 51, US Government Printing Office, 182 pp.

Oke, P.R., M.A. Balmaseda, M. Benkiran, J.A. Cummings, E. Dombrowsky, Y. Fujii, S. Guinehut, G. Larnicol, P.-Y. Le Traon, and M.J. Martin. 2009. Observing system evaluations using GODAE systems. Oceanography 22(3):144–153.

Roemmich, D., and the Argo Steering Team. 2009. Argo: The challenge of continuing 10 years of progress. Oceanography 22(3):46–55.

Smith, N. 2006. Perspective from the Global Ocean Data Assimilation Experiment. Pp. 1–17 in GODAE Summer School in “Ocean Weather Forecasting: An Integrated View of Oceanography.” E.P. Chassignet and J. Verron, eds, Springer, Lallonde les Maures, France.

Teague, W.J., M.J. Carron, and P.J. Hogan. 1990. A comparison between the generalized digital environmental model and Levitus climatologies. Journal of Geophysical Research 95:7,167–7,183.

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