glm-lake-model

name	glm-lake-model
description	Running the General Lake Model (GLM3) for lake temperature simulation, including configuration file structure and execution.

GLM Lake Model Skill

Overview

GLM (General Lake Model) is a 1D hydrodynamic model for simulating vertical water temperature, mixing, and stratification in lakes.

Installation

GLM binary is typically at /usr/local/bin/glm. Run with:

cd /path/to/simulation/dir
glm

GLM reads glm3.nml from the current directory.

Configuration File (glm3.nml)

Key sections:

• &glm_setup: Basic simulation parameters
• &light: Light extinction (Kw = light attenuation coefficient, m⁻¹)
• &mixing: Turbulent mixing parameters
  • coef_mix_hyp: Hypolimnetic mixing coefficient
  • coef_mix_conv, coef_wind_stir, coef_mix_shear, coef_mix_turb, coef_mix_KH
• &time: Simulation period (start, stop in 'YYYY-MM-DD hh:mm:ss')
• &output: Output directory and filename
• &meteorology: Met forcing file and factors
  • wind_factor: Scale wind speed
  • lw_factor: Scale longwave radiation
  • ch: Sensible heat transfer coefficient
  • sw_factor, cd, ce: Do NOT change these
• &init_profiles: Initial temperature/salinity profiles

Running GLM

cd /root  # Must run from directory containing glm3.nml
glm       # Reads glm3.nml, writes output per &output section

Output

• NetCDF file at output/output.nc with variables:
  • time: time in days since reference
  • z: layer heights (m above bottom)
  • temp: water temperature (°C) per layer
  • NS: number of active layers per timestep