A grid cell is divided into 5 primary land cover types: glacier, lake, wetland, urban and vegetation (see figure). An urban land cover is included so that future versions of the model can study urbanization, but currently the urban cover is zero. The vegetated portion of a grid cell is further divided into patches of up to 4 of 16 plant functional types (PFTs). Each PFT has its own leaf area index, stem area index, and canopy top and bottom heights. Not all grid cells contain 4 PFTs. Homogenous vegetation may have fewer PFTs (e.g., one) than mixed vegetation (e.g., four). Bare ground is represented not as a primary land cover type, but rather as an unvegetated patch occurring among the PFTs. Each subgrid land cover type and PFT patch is a separate column for energy and water calculations.

Each model grid cell also requires a soil color (which determines soil albedos) and soil texture (defined by percent sand and percent clay). The soil texture dataset allows vertical profiles of sand and clay.

The required surface data is illustrated here. The surface dataset includes: the glacier, lake, wetland, and urban portions of the grid cell (vegetation occupies the remainder); the fractional cover in the vegetated portion of the grid cell of the 4 most abundant PFTs; monthly leaf and stem area index and canopy top and bottom heights for each PFT; soil color; and soil texture. These fields are aggregated to the model's grid from high-resolution surface datasets (aggregation).

The relative areas of each sub-grid unit, plant functional type, and leaf area index are obtained from 1-km satellite data. See PFTs for more details.