UNCERTAINTIES ASSESSMENT FOR MERIS/OLCI FAPAR

摘要

This paper describes the procedure for estimating the uncertainties budget of the Fraction of Absorbed Photosynthetic Active Radiation (FAPAR) derived from both ENVISAT (Medium Resolution Instrument Sensor (MERIS) and Sentinel-3/Ocean Land Colour Instrument (OLCI). This product is obtained from daily Top Of Atmosphere (TOA) data in the blue, red and nearinfrared spectral bands. The algorithm itself takes the form of a set of several formulae which transform calibrated spectral bidirectional directional reflectances (BRFs) into a single numerical value. These formulae are designed to extract the direct green FAPAR in the plant canopy and the rectified channels in the red and near-infrared bands. Following the guidelines of Quality Assurance for Earth Observation (QA4EO) [1], the uncertainties are estimated using the uncertainties propagation theory which takes into account the one associated to the inputs, i.e. the spectral reflectance measurements at the top of the atmosphere. Methodology and results using simulated data and actual MERIS data are presented.