Tutorial: a modified simple example

The following is a brief tutorial for how to use the LOAM model and the pre- and post-processing tools which are available on our local SGI machines. The current version uses various local libraries, as described in the Introduction and Model Description and an in-house output format. We are in the process of creating a portable version of the model including all necessary library routines, which will produce standard format (netcdf, or equivalent) output files. The user could then use his/her favorite tools for creating input files and for viewing model output. Contact us if you are willing to beta test this version.

The best way for a new user to become acquainted with the new version of the model is to follow the example that has been set up in the directory NEW . The file simple.README within this directory contains instructions for setting up one's own working directory, linking to the NEW directory, and performing the example run for the Pacific domain. The parameter file which is to be used for the example run is simple. This is an ascii parameter file that is read by the model at execution time. It prescribes the shape of the horizontal domain, the vertical grid chosen, and the numerous parameter choices for the model run, as in the previous version.

Note the following changes, additions and deletions from the old version:

Obsolete Parameters

Nonlin : always nonlinear Thermo : temperature is always used to compute bouyancy Vert_Bot : sorry folks, no reduced gravity option Vert_Fix Vert_Sys : inferred from Nsigma

Modified Parameters

Nsigma : number of variable depth layers at the top NZ : total number of vertical levels/layers H_profile : use either this, or Z_profile to specify initial layer depths Z_profile : NZ values for the z levels (this will override H_profile specification) Z_bot : total depth (must specify when using Z_profile, but bathymetry data will override)

New Parameters


Bath_file : name of data file containing bathymetry Bathymetry : 0-constant(specified by Z_bot), 1-read from data 2-random values at each grid point, 3-ramp Bath_min : minimum allowed depth of topography (in meters) Bath_type : 0-bathymetry takes only z values, 3-last layer goes to bottom as defined by bathymetry data

Coordinate system

Y_stretch_type: 1-original 2-cos(y), for uniform aspect ratio (will be set by remap, along with NX, NY, etc)


Discretization: 2-second order 4-fourth order Upwind_cnst : vertical advection, 1.-original, >1 - more upwind

Barotropic Solver

Baro_nonlin : 1-turns off the nonlinear advection terms in baro mode (the default is 0- include everything) Antarctica : land south of -60 is a periodic island Antarctica_lat: latitude on which to do line integral Channel : southern boundary is a periodic island Channel_lat : controls latitude for line integral Iceland : 0-ignore island; 1-standard island; 2-sink island) Australia : 0-ignore island; 1-standard island; 2-sink island) Other_island : specify [alon,blon,alat,blat,type(as above)] )

Shapiro Filter, new parameters

Shap_vel_damp : coefficient for momentum (between 0 and 1) Shap_scl_damp : coefficient for tracers (between 0 and 1)

Isopycnal Diffusion/ Gent-McWilliams eddy parameterization

Diffiso_scl : 1-use explicit diffusion on tracers;0-don't Diffiso_vel : 1-use explicit diffusion on momentum;0-don't Diffiso_alpha : 0.-pure horizontal; 1.-pure isopycnal Diffiso_coef : coef of isopycnal diffusion Diffiso_eps : ratio of diapycnal/isopycnal diffusion Diffiso_cadv : coef of diffusion for Gent-McWilliams


Ice : 1-compute ice; 0- no ice Ice_dynamics : 1-move ice; 0- static ice


Clim_TS : 0-not used; 1-Const. in time; 2-Vary;) Clim_coef : time scale of relaxation (days) Clim_relax : 0-no relaxation; 1-South-North; 2-Total; 3-general Pre_proc : 1-convectively adjust sponge data before using 0-don't Sponge_width : sponge width (number of grid points)