# Summary of Solar Fluxes

## Canopy Radiative Transfer

The article discusses the direct beam and diffuse fluxes in the canopy, as illustrated in Figure 2.4.1. It introduces various radiative flux terms, such as upward and downward diffuse fluxes, direct beam flux transmitted through the canopy, and fluxes absorbed by the vegetation.

## Calculating Solar Radiation Absorbed

The total solar radiation absorbed by the vegetation and ground is calculated using equations 2.4.1 and 2.4.2. For non-vegetated surfaces, the absorbed solar radiation is calculated using equation 2.4.3.

## Sunlit and Shaded Leaves

The article explains how the absorbed photosynthetically active radiation is apportioned to the sunlit and shaded leaves, using equations 2.4.5 and 2.4.6. The sunlit plant area index is calculated using equation 2.4.7, with the parameter K determined by equation 2.4.8.

## Two-Stream Approximation

The model uses the two-stream approximation to calculate radiative transfer of direct and diffuse radiation through the canopy, with an optional multi-layer canopy approach. The derivatives of the absorbed radiative fluxes with respect to plant area index are used to derive the light profile within the canopy.