  The review describes the development of ideas Gury Ivanovich Marchuk in the
field of variational data assimilation for ocean models applied in particular
in coupled models for long-range weather forecasts. Particular attention is
paid to the optimization of boundary conditions on rigid boundaries. As
idealized and realistic model configurations are considered. It is shown that
the optimization allows us to determine the most sensitive model operators and
bring the model solution closer to the assimilated data.
