1 research outputs found
Variational assimilation of Lagrangian data in oceanography
We consider the assimilation of Lagrangian data into a primitive equations
circulation model of the ocean at basin scale. The Lagrangian data are
positions of floats drifting at fixed depth. We aim at reconstructing the
four-dimensional space-time circulation of the ocean. This problem is solved
using the four-dimensional variational technique and the adjoint method. In
this problem the control vector is chosen as being the initial state of the
dynamical system. The observed variables, namely the positions of the floats,
are expressed as a function of the control vector via a nonlinear observation
operator. This method has been implemented and has the ability to reconstruct
the main patterns of the oceanic circulation. Moreover it is very robust with
respect to increase of time-sampling period of observations. We have run many
twin experiments in order to analyze the sensitivity of our method to the
number of floats, the time-sampling period and the vertical drift level. We
compare also the performances of the Lagrangian method to that of the classical
Eulerian one. Finally we study the impact of errors on observations.Comment: 31 page