  A 4D-Var data assimilation technique is applied to a ORCA-2 configuration of
the NEMO in order to identify the optimal parametrization of the boundary
conditions on the lateral boundaries as well as on the bottom and on the
surface of the ocean. The influence of the boundary conditions on the solution
is analyzed as in the assimilation window and beyond the window. It is shown
that optimal conditions for vertical operators allows to get stronger and finer
jet streams (Gulf Stream, Kuroshio) in the solution. Analyzing the reasons of
the jets reinforcement, we see that the major impact of the data assimilation
is made on the parametrization of the bottom boundary conditions for lateral
velocities u and v. Automatic generation of the tangent and adjoint codes is
also discussed. Tapenade software is shown to be able to produce the adjoint
code that can be used after a memory usage optimization.
