Summary:

### Initialization of Land Model

The initialization of the land model in the Community Land Model (CLM) depends on the type of run - startup or restart. In a startup run, the model can be initialized using:

1. Arbitrary initial conditions set internally in the Fortran code.
2. An initial conditions dataset that enables the model to start from a spun-up state.

In a restart run, the model is continued from a previous simulation and initialized from a restart file.

#### Arbitrary Initial Conditions

The arbitrary initial conditions are specified as follows:

- Soil points are initialized with surface ground temperature (274 K), soil layer temperature (274 K), vegetation temperature (283 K), no snow or canopy water, and volumetric soil water content (0.15 mm³/mm³ for top layers, 0.0 mm³/mm³ for lower layers).
- Lake temperatures are initialized at 277 K with no snow.
- Glacier temperatures are initialized at 250 K with a snow water equivalent of 1000 mm and a snow depth calculated from the snow density (250 kg/m³). The snow layer structure is initialized based on the snow depth.
- The snow and soil liquid water and ice contents are initialized based on the temperature and soil moisture conditions.
- All vegetated and glacier land units are initialized with water stored in the unconfined aquifer (4000 mm) and a water table depth of 5 meters below the soil column.