CCSM/LANL Parallel Ocean Program (POP)
Entry ID: LANL-POP
Abstract: POP is an ocean circulation model derived from earlier models of Bryan, Cox,
Semtner and Chervin in which depth is used as the vertical coordinate. The
model solves the three-dimensional primitive equations for fluid motions on the
sphere under hydrostatic and Boussinesq approximations. Spatial derivatives are
computed using finite-difference discretizations which are ... formulated to handle
any generalized orthogonal grid on a sphere, including dipole and tripole grids
which shift the North Pole singularity into land masses to avoid time step
constraints due to grid convergence.
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
A wide variety of physical parameterizations and other features are available
in the model and are described in detail in a reference manual distributed with
the code. Because POP is a public code, many improvements to its physical
parameterizations have resulted from external collaborations with other ocean
modeling groups and such development is very much a community effort. Detailed
descriptions of the numerical discretizations and methods are described in the
reference manual and in other publications.
Although POP was originally developed for the Connection Machine, it was
designed from the start for portability by isolating all routines involving
communication into a small set (5) of modules which can be modified for
specific architectures. Currently, versions of these routines exist for MPI and
SHMEM communication libraries and also for serial execution. The appropriate
directory is chosen at compile time and no pre-processor directives are used to
support different machines. Support for hybrid programming using threads and
message passing has recently been added and is described in the User's Guide.
POP is the ocean component of the Community Climate System Model and has been
used extensively at LANL in ocean-only mode for eddy-resolving simulations of
the global ocean and for ocean-ice coupled simulations with the CICE model.
The CCSM3.0 POP is based upon POP Version 1.4.3, which was developed at Los
Alamos National Laboratory. Over the course of CCSM3 POP model development,
there have been many small changes to the original POP 1.4.3 code in order to
allow the code to conform to CCSM requirements. Also, some corrections have
been applied, diagnostics have been added, and more substantial modifications
have been made to the code to improve the model physics. Wherever possible, a
deliberate effort has been made to alter the base POP 1.4.3 code as little as
possible, mainly by adding new modules instead of integrating the additions
into the original POP code. However, many of the CCSM-related requirements
resulted in modifications to numerous existing POP modules.
POP is freely available to the community (under a copyright agreement); you can
download the latest version from these pages.
(Summary adapted from LANL.)
Use Constraints The CICE code is freely available under a copyright agreement. Atmospheric
forcing data for 1997 are also available. These data files are designed only
for testing the code and are not necessarily the best observational data.
Please do not publish results based on these data sets.
The POP compponent of the CCMS3.0 is available, but users must register first
and agree to the copyright notice and distribution:
for a complete list of references.
Creation and Review Dates