Biophysical Processor Overview |

The Biophysical Processor computes Level-2B Biophysical products from Sentinel-2 or LANDSAT 8 reflectances. From top-of-canopy normalized reflectance data, it derives a set of biophysical variables, namely :

- LAI : Leaf Area Index
- FAPAR : Fraction of Absorbed Photosynthetically Active Radiation
- FCOVER : Fraction of vegetation cover
- Cab : Chlorophyll content in the leaf
- CW : Canopy Water Content

The biophysical variable retrieval algorithm is based on specific radiative transfer models associated with strong assumptions, particularly regarding canopy architecture (turbid medium model). All the variables derived from such algorithms should be seen as effective, i.e. the variables that would correspond to the measured satellite signal reflected by a canopy verifying all the assumptions made through the radiative transfer models. Depending on the variable, this may lead to differences with ground values that may be accessed from field measurements.

Furthermore, the algorithm is "generic", i.e. it should apply to any type of vegetation with reasonable performances. However, to better match the specificities of given canopies, either simple correction could be calibrated, or more specific algorithm could be developed.

One strong assumption embedded in any single pixel retrieval algorithm as this one, is that the pixel targeted belongs to a landscape patch presenting enough homogeneity (at the pixel scale) preventing unexpected loss or gain of radiation fluxes. For forests with large crowns, or any pixel showing strong heterogeneity such as pixels at the intersection between two different vegetation patches, results may be uncertain. This applied also to pixels where the neighbouring ones are very different. Specific algorithms should be developed to detect such situations and possibly propose alternative retrieval methods.

Sentinel-2 Processor Documentation

Sentinel-2 10m Processor Documentation

LANDSAT 8 Processor Documentation

Algorithm Specification