Long-Term Measurements of Plant Phenology Over Europe Derived from SeaWiFS and MERIS
Ceccherini, Guido; Gobron, N.; Migliavacca, M.; Robustelli, M.

Since its launch in April 2002, the Medium Resolution Imaging Spectrometer Instrument (MERIS) on board ENVIronmental SATellite (ENVISAT) provided accurate spectral measurements, which have been used for deriving terrestrial geophysical parameters such as the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR). This paper examines plant phenology over the European domain over the last 14 years using FAPAR derived from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data (1998-2002) and MERIS (2003-2011). The analysis first focuses on the definition of a method to extract key phenological variables from space-derived FAPAR. Three vegetation phenological metrics, namely start of growing season, growing season length and end of growing season have been then computed over Europe. We check the performance of our phenology metrics by comparing them against ground-based observation over ecological sites (i.e. Fluxnet and PEP725). Results suggest that plant phenology derived from earth observation agrees well with that of in-situ measurements, although quantifying the end of the growing season presented some uncertainties. Over this period, such metrics can track simple, yet critical, impacts of climate change on ecosystems. Similar studies with the similar FAPAR product deriving from the future Ocean and Land Color Instrument (OLCI) on board Sentinel-3 will serve for continuously monitoring the phenology.