Lorenz system

Author: A. Lawless, M. Martin and M. Wlasak

Software requirements: Matlab

Fluctuations of the quantities (x,y,z) of the three-variable Lorenz system.

Several different assimilation schemes are coded for the three-variable Lorenz system. For each of them identical twin experiments can be run and compared for different assimilation and observation parameters. The documentation provides a series of suggested exercises. All the programs use the routine menu_asl.m, which is an altered version of the standard menu routine and must be downloaded with the main programs.

• pdf documentation
• menu_asl.m - Source for menu routine

Sequential schemes

• lorenz_menu.m - Program source, top level

4D-Var and incremental 4D-Var

• lorenz4d.m - Top level routine for full 4D-Var
• lorenz4d_inc.m - Top level routine for incremental 4D-Var
• calcfg.m - Calculate cost function and its gradient for full 4D-Var
• calcfg_inc.m - Calculate cost function and its gradient for incremental 4D-Var
• modeuler.m - Non-linear model for Lorenz system, using modified Euler scheme
• modeuler_tl.m - Tangent linear model
• modeuler_adj.m - Adjoint model
• test_tl.m - Test tangent linear model
• test_adj.m - Test adjoint model
• test_grad.m - Test of calcfg
• test_gradinc.m - Test of calcfg_inc