Open boundary conditions for Lagrangian geophysical fluid dynamics

Initial-boundary-value problems for the hydrostatic primitive equations of meteorology and oceanography are ill-posed if the boundaries are open and fixed in space (Oliger and Sundstrom, 1978). It is shown here with theory and computation that the same problems are well-posed if the open boundaries are comoving, that is, if they move with the fluid particles. Comoving or Lagrangian coordinates are then particularly convenient. These findings will expedite the variational assimilation of Lagrangian data. (C) 1999 Academic Press.