Data assimilation of photosynthetic light-use efficiency using multi-angular satellite data: I. Model formulation

► Presents a new theoretical framework for forest GPP. ► Companion paper evaluates approach over a diverse array of forested ecosystems. ► GPP model employs multi-angle spectral measures of vegetation e from CHRIS/PROBA. ► GPP model treats shaded and sunlit canopy components individually. ► GPP model down-regulates e half hourly using multivariate function of D, T and PAR.