Summary:

Phenology and Vegetation Burial by Snow

The biogeochemistry model in the article updates leaf and stem area indices (LAI and SAI) daily by linearly interpolating between monthly values. The monthly PFT (plant functional type) LAI values are derived from MODIS satellite data, and the SAI is calculated from the LAI using established methods.

The leaf and stem area indices are then adjusted to account for vertical burial by snow. This is done using the equation:

A = A* (1 - fveg^sno)

Where A* is the original LAI or SAI, A is the remaining exposed leaf or stem area, and fveg^sno is the vertical fraction of vegetation covered by snow.

The fraction of vegetation covered by snow (fveg^sno) is calculated differently for trees/shrubs versus grasses/crops. For trees and shrubs, it is the ratio of the snow depth minus the height of the bottom of the vegetation, divided by the height of the top of the vegetation minus the bottom. For grasses and crops, it is the minimum of the snow depth and the critical snow depth (0.2 m) divided by the critical snow depth.

If the exposed leaf and stem area is less than 0.05, it is set to zero, and the surface is treated as snow-covered ground.