2.5.2 Physics and analysis tools

Other features which are new to MOM 2 relative to MOM 1 include the following.

1.

Various modules can be exercised alone or as part of a fully configured model, as discussed in Chapter 15.

2.

An integrated DATABASE is described in Chapter 13 along with run_scripts in Section 3.2 which will automatically prepare this data for any of the configurations and arbitrary resolutions of MOM 2.

3.

Chapter 19 details a generalized surface boundary condition interface which handles all surface boundary conditions as if they come from a hierarchy of atmospheric models. This includes simple datasets which are fixed in time through complicated atmospheric GCM's. Mismatches in geometry and resolution between atmospheric GCM's and MOM 2 are automatically taken care of. However, since linear interpolation is used to apply atmospheric fluxes to MOM 2, the fluxes are not stricly conserved.

4.

Elliptic equation solvers for the external mode have been re-worked to be more accurate and give speedier convergence as discussed in Section 22.11.

5.

The vertical velocity fields have been reformulated to prevent numerical separation in the presence of sharp topographic gradients as described in Section 22.3. The grid is constructed by a module which allows for a MOM 1 type construction with grid points always in the center of tracer cells on non-uniform grids or a new way with grid points always in the center of velocity cells on a non-uniform grids. Both are second order accurate if the stretching function is analytic and are described in Chapter 16.

6.

All diagnostics have been re-written to be more modular, old ones have been improved, many new ones added (such as reconstructing the surface pressure from the stream function, calculating particle trajectories, time averaged fields, xbt's etc.), and all are described in Chapter 38.

7.

The prognostic surface pressure and implicit free surface methods of Dukowicz and Smith (1993,1994) have been implemented.

8.

The isoneutral diffusion scheme of Griff ies et al. (1998) has been implemented.

9.

The eddy advection of Gent and McWilliams (1990) has been implemented, with numerics made consistent with the new isoneutral diffusion formulation.

10.

Options for tracer advection include the traditional centered differences, a fourth order advection scheme taken from Mahlman's stratospheric code (SKYHI), the FCT scheme of Gerdes, Köberle and Willebrand (1991), a third order advection scheme (by Holland) very similar to the Quick scheme of Leonard (1979).

11.

The pressure gradient averaging technique of Brown and Campana (1978).

12.

Neptune effect of Holloway (1992).

13.

Rigid grid rotation; i.e., rotate poles, while keeping the identical lat/lon structure.

14.

Open boundaries of Stevens (1990).

15.

The discretization of vertical mixing of Pacanowski/Philander (1981) has been changed to yield more accurate and stable solutions as indicated in Section 32.2.4.

16.

Some restructuring of the memory window logic to allow for a more robust implementation of parallelism and fourth order schemes.

17.

There are also more options for configuring MOM as described in Part XIV and many other little features and code improvements too numerous to summarize here but covered in this manual.

Some of the differences between MOM 2 version 1 and version 2 are as follows.

1.

All diagnostics have been given an interface to generate NetCDF formatted output as described in Chapter 38. The NetCDF format allows easy access to results without writing intermediate analysis code. The recommended way to visualize results is to use Ferret which is a graphical analysis tool developed by Steve Hankin (1994) at NOAA/PMEL
email: ferret@pmel.noaa.gov
web: http://www.pmel.noaa.gov/ferret/home.html

2.

Uni-tasking is discussed in Chapter 11 and multi-tasking is discussed in Chapter 12.

3.

Since the arrival of a CRAY T90 and Unicos 9 operating system in August 1996, there is no longer a CRAY Fortran 77 compiler. It has been replaced by a Fortran 90 compiler which for the most part is compatible with ``cf77''. The minimum requirement for MOM is now Fortran 90.