POP
The Parallel Ocean Program is an ocean circulation model developed at LANL capable of ocean simulations as well as coupled atmosphere, ice, and land climate simluations. Time integration of the model is split into two parts. The three-dimensional vertically-varying (baroclinic) tendencies are integrated explicitly using a leapfrog scheme. The very fast vertically-uniform (barotropic) modes are integrated using an implicit free surface formulation in which a preconditioned conjugate gradient solver is used to solve for the two-dimensional surface pressure.
