Here is a summary of the article "2.2. Surface Characterization, Vertical Discretization, and Model Input Requirements" from the CTSM master documentation:

Surface Characterization and Vertical Discretization
- The Community Terrestrial Systems Model (CTSM) requires detailed information about the surface characteristics and vertical layering of the land surface.
- Surface characteristics include vegetation type, soil properties, and topography, which are used to model processes like radiation, hydrology, and biogeochemistry.
- The vertical discretization defines the number and thickness of soil layers, which impacts how water, energy, and carbon are transported through the soil profile.

Model Input Requirements
- CTSM requires several input datasets to specify the surface characteristics and vertical discretization, including:
  - Land cover/plant functional type distribution
  - Soil properties (texture, color, organic matter, etc.)
  - Elevation, slope, aspect
  - Number and thickness of soil layers
- These input datasets are usually provided at a spatial resolution matching the model grid, and may require preprocessing and aggregation.
- Careful specification of these inputs is critical for accurate representation of land surface processes in the CTSM model.