5.1.3 - Fraction of photosynthetically active radiation (fAPAR)

FAPAR represents the fraction of incoming solar radiation in the photosynthetically active radiation (PAR) spectral range (0.4 - 0.7 μm) that is absorbed by the green parts of the canopy.



fAPAR has been recognized as one of the fundamental terrestrial state variables in the context of the global change sciences (Steering Committee for GCOS, 2003; Gobron et al., 2006). It is a key variable in models of vegetation primary productivity and, more generally, in carbon cycle models implementing up-to-date land surfaces process schemes (e.g., Sellers et al., 1997). Besides, it is an indicator of the health of vegetation (Fraction of Absorbed Photosynthetic Active Radiation Product User Manual (PUM)).

Seasonal variations in LAI and fAPAR are vital to determine landscape water, energy and carbon balances, as well as in the detection of long-term climate change (Potter et al, 1993, Churkina and Running 1998, cited by Huemmrich et al, 2005).

FVC, LAI and fAPAR are currently estimated from SEVIRI on board MSG (METEOSAT SECOND GENERATION), within the framework of the LSA SAF. The LSA SAF is part of the EUMETSAT SAF Network.


The following programs have also implemented algorithms in their operational lines to provide advanced biophysical products:

  • POLDER (Leroy et al. 1997, Roujean and Lacaze 2002);
  • MODIS and MISR (Knyazikhin et al. 1999);
  • MERIS (Gobron et al. 1999, Bacour et al. 2006, Baret et al. 2007);
  • SEAWIFS (Gobron et al. 2001);
  • VEGETATION (Baret et al. 2007, Bartholomé et al. 2006);
  • GLOBCARBON (Plummer et al. 2006, Deng et al. 2006)