The feasibility of deriving photosynthetically active radiation (PAR) from satellite observations on global scale was previously demonstrated (Pinker and Laszlo, 1992). The methodology used was evaluated against available ground truth (Pinker et al., 1993). The objective of this study was to provide, for a first time, consistent information on the temporal and spatial variability in PAR on a continental scale during a growing season; such information can be used to develop new parameterizations of net primary productivity and evapotranspiration, that till now were not possible. ¿ American Geophysical Union 1994