Meris Global Vegetation Index: Evaluation and Performance

This paper overviews the evaluation and the performance of the Medium Resolution Imaging Spectrometer (MERIS) Global Vegetation Index (MGVI) algorithm which is implemented in the MERIS ground segment as the main land surface product, also called the Top Of Atmosphere Vegetation Index (TOAVI). MGVI values represent the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) which act as an integrated indicator of the state of the plant canopy and can be retrieved by remote sensing techniques with acceptable accuracy. FAPAR can be used to quantify the presence of vegetation with good reliability on a global scale. The retrieval algorithm is optimized to be insensitive to atmospheric and angular effects as well as sensor spectral properties. The evaluation of the algorithm consists of comparisons of daily FAPAR values time series derived from MERIS against values derived from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data acquired over local sites in Europe during the year 2003. Scatter-plots of contemporaneous product values are analyzed, taking illumination and viewing geometries into account. We also investigate time series of FAPAR to demonstrate the feasibility of monitoring vegetation in the context of land application.