The GLM configuration file

A GLM model simulation is controlled through a main configuration file, written in Fortran namelist format.

Which file does GLM read?

If no file is given on the command line, GLM 4 looks for the following names in order, and uses the first one it finds in the working directory:

1. glm4.nml
2. glm3.nml
3. glm2.nml

This means existing GLM 3 configurations continue to work under GLM 4 — an unchanged glm3.nml will be picked up automatically. The example simulations in glm-examples are still supplied as glm3.nml for this reason.

To use a configuration file with any other name, pass it explicitly:

glm --nml mysim.nml

Note

There is no file named plain glm.nml. Earlier versions of this page referred to one; the actual defaults are the three names listed above.

Structure of the file

The key elements of this file are depicted as "blocks", each introduced by &blockname and terminated by /. Every block, with its options, types, units, defaults and a worked example, is set out in the configuration reference.

The reference covers the fourteen blocks below; follow a link to jump straight to one.

Model configuration	&glm_setup · &mixing · &wq_setup · &morphometry · &time · &output · &init_profiles · &light · &bird_model · &sediment · &snowice
Boundary conditions	&meteorology · &inflow · &outflow

Note

The reference documents the GLM 3 configuration. It remains broadly accurate for GLM 4, but the 4.x line adds options that are not yet covered there — including the in-core bubbler/destratification and oxygenation modules, and the reworked surface heat exchange module. Configuration options may still change ahead of the tagged 4.0.0 release.

Water quality configuration

If water quality is enabled, the &wq_setup block selects the library and its configuration file, via wq_lib and wq_nml_file. See Customising the WQ setup.