COMBINING AGRICULTURAL CROP MODELS AND SATELLITE-OBSERVATIONS - FROM FIELD TO REGIONAL SCALES

This review article gives an overview of how satellite observations ar e used to feed or tune crop models and improve their capability to pre dict crop yields in a region. Relations between crop characteristics w hich correspond to models state variables and satellite observations a re briefly analysed, together with the various types of crop models co mmonly used. Various strategies for introducing short wavelength radio metric information into specific crop models are described, from direc t update of model state variables to optimization of model parameter v alues, and some of them are exemplified. Methods to unmix crop-specifi c information from mixed pixels in coarse resolution-high frequency im agery are analysed. The conditions of use of the various methods and t ypes of information are discussed.