Operational NOAA vegetation indices-absorbed PAR relationships for Sahelian vegetation canopies

In order to improve the estimation of primary production at a regional scale through a better assessment of the fraction of Absorbed PAR (fAPAR) from spectral vegetation indices (VI), the case of the Sahelian vegetation is investigated using a 3D radiative transfer model. Simulations are conducted for two types of structurally distinct vegetation canopies (millet crops and savannas) and according to NOAA/AVHRR specifications. The results of the simulations show that the fAPAR-IV relationship is sensitive to the geometry of the measurement and the soil optical properties, especially in the case of the millet crop. The MSAVI gives the best results in terms of stability and linearity of the relation. This study is finally illustrated by an example of application to a NOAA-time series