Abstract:

Biomass is one of the key indicators in crop condition monitoring, which can reflect the growth status of crop and can be closely related to crop yield. One of the methods for retrieving biomass from remotely sensed observations is through inversion of microwave canopy reflectance models based on vector radiative transfer equation. Many model inversion methods fail to account for variable biomass values at different crop growth stages. The objective of this preliminary study is to assimilate the biomass information retrieved from SAR data into the crop growth model to describe the biomass changes with crop growth and improve the accuracy of biomass estimation. Firstly the relationship of temporal biomass with backscatter coefficients retrieved from SAR data is analyzed, and then an empirical model is developed to estimate biomass. Then the Fletcher-Reeves method is developed to modify the parameters of the model by minimizing the difference between biomass simulated by the crop growth model and biomass inverted by SAR data. The results showed that simulated biomass values by the revised model introduced SAR data and the measured values were consistent, and the estimated biomass profile had been significantly improved. And the assimilation of real time and dynamic SAR data into crop growth model can calibrate crop model to actual crop growth conditions to improve accuracy of simulated biomass.