GEOV2/VGT: near real time estimation of global biophysical variables from VEGETATION-P data
Résumé
The GEOV2 algorithm for continuous, consistent and near real time estimation of Leaf Area Index (LAI), fraction of absorbed photosynthetic active radiation (FAPAR) and vegetation cover fraction (FCOVER) from daily VEGETATION-P satellite data is here described. It consists of a series of procedures including (1) neural networks for providing instantaneous estimates from VGT-P reflectances, (2) a multi-step filtering approach to eliminate contaminated data mainly affected by atmospheric effects and snow cover, and (3) temporal techniques for ensuring consistency and continuity as well as short term projection of the product dynamics. First validation results show that GEOV2/VGT products have high consistency with previous GEOV1/VGT products and show similar accuracy levels as compared to ground measurements. GEOV2 significantly improves GEOV1 in terms of continuity (less than 1% of missing data in GEOV2 as compared to the 20% of gaps in GEOV1) and consistency (smoother products less affected by noise in the data), specially at high latitudes and Equatorial areas. Global GEOV2/VGT products at 1/112 degrees spatial resolution for the period 1999-present with near real time estimates every 10 days will be freely available at Copernicus portal (http://land.copernicus.eu).