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Ocean Science An interactive open-access journal of the European Geosciences Union
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Volume 8, issue 2 | Copyright
Ocean Sci., 8, 249-259, 2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 30 Mar 2012

Research article | 30 Mar 2012

Variational assimilation of Lagrangian trajectories in the Mediterranean ocean Forecasting System

J. A. U. Nilsson1,*, S. Dobricic2, N. Pinardi3, P.-M. Poulain4, and D. Pettenuzzo1 J. A. U. Nilsson et al.
  • 1National Institute of Geophysics and Vulcanology (INGV), Via Donato Creti 12, 40128 Bologna, Italy
  • 2Centro EuroMediterraneo per i Cambiamenti Climatici (CMCC), Bologna, Italy
  • 3Corso di Scienze Ambientali, Bologna University, Ravenna, Italy
  • 4The National Institute of Oceanography and Applied Geophysics (OGS), Trieste, Italy
  • *now at: Climate Modeling and Impacts Lab (UTMEA-ENEA), Rome, Italy

Abstract. A novel method for three-dimensional variational assimilation of Lagrangian data with a primitive-equation ocean model is proposed. The assimilation scheme was implemented in the Mediterranean ocean Forecasting System and evaluated for a 4-month period. Four experiments were designed to assess the impact of trajectory assimilation on the model output, i.e. the sea-surface height, velocity, temperature and salinity fields. It was found from the drifter and Argo trajectory assimilation experiment that the forecast skill of surface-drifter trajectories improved by 15 %, that of intermediate-depth float trajectories by 20 %, and moreover, that the forecasted sea-surface height fields improved locally by 5 % compared to satellite data, while the quality of the temperature and salinity fields remained at previous levels. In conclusion, the addition of Lagrangian trajectory assimilation proved to reduce the uncertainties in the model fields, thus yielding a higher accuracy of the ocean forecasts.

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