Summary of the Lake Model Article:

Title: Lake Model - CTSM CTSM Master Documentation

Main Points:

1. Lake Model Overview:
   - The lake model, called the Lake, Ice, Snow, and Sediment Simulator (LISSS), is based on extensive modifications to the lake code used in previous versions of the Community Land Model (CLM).
   - The lake model incorporates concepts from various other lake models, including those by Bonan, Henderson-Sellers, Hostetler, and others.

2. Lake Characteristics:
   - Lakes have spatially variable depth prescribed in the surface data.
   - The surface data can optionally include lake optical extinction coefficient and horizontal fetch, currently used only for site simulations.

3. Lake Physics:
   - The model simulates freezing and thawing in the lake body, with resolved snow layers, soil layers, and bedrock layers below the lake body.
   - Temperatures and ice fractions are simulated for 10 layers (for global simulations) or 25 layers (for site simulations).

4. Lake Surface Processes:
   - Lake albedo is described in section 2.12.3.
   - Lake surface fluxes follow the formulations for non-vegetated surfaces, with the lake surface temperature (representing an infinitesimal interface layer) solved simultaneously with the surface fluxes.
   - After surface fluxes are evaluated, temperatures are solved simultaneously in the resolved snow layers, the lake body, and the soil and bedrock, using the ground heat flux as a top boundary condition.

5. Integration with Soil and Snow Models:
   - The snow, soil, and bedrock models generally follow the formulations for non-vegetated surfaces, with modifications described in the document.