1-layer linear shallow water model

The model integrates the linearized shallow water equations (ref. equation 3.112 in "Atmospheric and Oceanic Fluid Dynamics" by Vallis, 4th Ed.) on a C-grid. The first time step is Euler forward (using information in step 1 to get to step 2). The following steps are done by a leap frog scheme (using information in step n-1 and n to get to n+1). The "nt" time steps are divided into "nsubcycles" steps. Thus, the model computes nt*nsubcycles steps, but only saves nt steps.

This model is intended as a minimal example of an atmosphere or ocean model. It is written in Fortran 90 with netCDF support.

Authors

Joakim Kjellsson & Laurent Brodeau

Prerequisites

Install a Fortran compiler (Mac OS):

Download MacPorts and follow instructions to install.
Then install GCC. In this case we use GCC v13 (but any later version should be fine too):

sudo port install gcc13

If you chose to install MacPorts in /opt/local/ you should now have /opt/local/bin/gfortran-mp-13 (assuming you installed v13).

Install netcdf (optional):

sudo port install netcdf netcdf-fortran

You should now have the netCDF Fortran libraries in /opt/local/lib/. You should set NCDF_ROOT=/opt/local/ in the makefile.netcdf.

Install a Fortran compiler (Linux): 1a) Use apt-get (Ubuntu, Linux Mint, etc)

sudo apt-get install gfortran

1b) Use yum (Fedora, Red Hat etc)

sudo yum install gcc-gfortran

Install netcdf (optional)

sudo apt-get install netcdf netcdf-fortran

(or similar with yum)

Install Fortran compiler (Windows):

Install Linux and follow instructions above ;-)

Compile the model

If you want netCDF support use the makefile.netcdf, otherwise use makefile.binout. Which ever you choose you will need to set the following:

FC = gfortran (or whatever your compiler name is)
NCDF_ROOT = /opt/local/ (or whereever your netcdf is installed)

Note: You can usually find the netcdf directory with the command

nf-config --prefix

Now compile with make -f makefile.netcdf (for netcdf) or make -f makefile.binout (without netcdf).

Running the model

To run the lab3 experiment (geostrophically balanced flow on a beta plane):

Link the namelist to a file namelist

ln namelist_lab3 namelist

Run the model

./shallowwater_lab3.x

Changing model parameters

Model parameters are controlled via namelists, which are text files that Fortran reads. The model will always read the file namelist, which can be a link to another file, e.g. namelist_lab1. The model sets a lot of variables by default, e.g. domain size, Coriolis parameter etc, but the namelist overwrites the model defaults. The model parameters should therefore be changed by changing the namelist, not the model code.

Output

Results will be saved to u_test.nc, v_test.nc and h_test.nc netCDF files.