The use of radiative transfer models for remote sensing data assimilation in crop growth models

The raster based PROMET-V model calculates spatial distributions of crop growth, water, carbon and nitrogen. The total leaf area index (LAI), the fraction of brown leaves in the canopy and surface soil moisture, as modelled in PROMET-V, were used in conjunction with the radiative transfer model GeoSAIL to model surface reflectance spectra of the main agricultural land use classes. By minimising the difference between observed reflectance spectra derived from optical remote sensing and the modelled surface reflectance spectra, the LAI, fraction of brown leaves and surface soil moisture were estimated. PROMET-V is then re-initialised until retrieved and simulated LAI match. This assimilation procedure leads to improved model results regarding biomass and yield. Thus remote sensing supports the crop growth model to simulate the observed spatial variability of the canopy. This information is can serve as important input to PA.