Summary:

Overview of Lake Hydrology in the Model

The article discusses the hydrological modeling of lake columns in the land surface model. Key points:

Hydrology of Lake Columns
- Similar to modeling of other impervious, non-vegetated columns (e.g., glaciers)
- Snow layers are resolved, but no infiltration into the permanent ground is allowed
- Water mass of lake columns is kept constant, except for overlying snow
- A generalized runoff term (qrgwl) is used to balance the water budget

Modifications to Soil and Snow Parameterizations
- Soil can freeze/thaw and allow for frost heave, but no air-filled pore space
- Two changes to the snow model for numerical stability:
  1. Dew/frost absorption by completely melted top snow layer is not allowed
  2. Minimum snow layer thickness is set to 4 cm (instead of 1 cm) to meet the CFL condition with the default 1800s timestep

The summary highlights the key aspects of how the hydrology of lake columns is modeled, including the treatment of soil, snow, and the water budget, as well as the specific modifications made to the snow parameterization for numerical stability.