Istituto di Scienze Marine     
Taillandier V., Griffa A., Molcard A. A variational approach for the reconstruction of regional scale Eulerian velocity fields from Lagrangian data. In: Ocean Modelling, vol. 13 (1) pp. 1 - 24. Elsevier, 2006.
A method for the reconstruction of the mesoscale Eulerian velocity field based on Lagrangian data at given sampling period is presented. A variational approach is used, where information on the float positions are combined with a simple model constraint describing the motion of particles advected in a velocity field. The velocity field of a priori specified space scale is estimated minimizing a cost function which measures the distance between the observed float positions and the model predicted ones for each sampling period. The method is first implemented considering the time-independent approximation of the velocity correction during a time interval shorter than the typical time scale of the mesoscale field. In a second step, this approximation is relaxed to consider inertial oscillations superimposed on the mesoscale field. The method is tested on a numerical regional circulation on the Northwestern Mediterranean Sea, characterized by an Eulerian time scale significantly longer than the inertial period. The observational coverage of the region varies between 80% and 16% and the corresponding error in the velocity reconstruction varies from less than 10% to approximately 50%, with a sampling period of the day. For smaller sampling intervals, the reconstruction is further improved in the time-dependent approximation. Finally, the method is used to combine information from Lagrangian data and General Circulation Models. The results suggest the useful application of the method for assimilation studies. (c) 2005 Elsevier Ltd. All rights reserved.
DOI: 10.1016/j.ocemod.2005.09.002
Subject tropical pacific-ocean
data assimilation system
mean flow decomposition
drifter data
surface circulation
adriatic sea
meteorological observations

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