Evaluation of methods to compute green-up dates based on daily NDVI observations

Area-wide green-up dates for Central and Western Europe could be derived for all methods and years (exemplary s. Figure 1). Phenological metrics are in accordance with climatic and topographic conditions: an early start-of-the-season for southwestern Europe and a later green-up towards Central and Eastern Europe as well as the elevated regions of the Pyrenees, the Alps, the Apennines and the Carpathians. Large coniferous woodlands such as in southwestern France or regions of intense agriculture/dense canal networks (Po and Rhine Valley, Netherlands) are attributed fairly late green-up dates which should be investigated further. Computed green-up days are in line with respective budburst events observed on the ground for the area of Germany.