Retrieval of Leaf Area Index by Coupling Radiative Transfer Model and a Dynamic Model

A new algorithm is developed to estimate LAI from time-series MODIS reflectance data (MOD09A1) based on coupled radiative transfer model and process model. The radiative transfer model is coupled with an empirical LAI dynamic model to simulate the time series reflectances. An optimization method is used to adjust the values of the parameters of the coupled model to seek a model trajectory that best fits a set of observations in a given time window. The preliminary analysis using MODIS surface reflectance data at some fluxnet sites was performed to validate this method. The results show that the algorithm is able to produce spatially and temporally continuous LAI product efficiently, and the accuracy of the retrieved LAI has been significantly improved over the MODIS LAI product compared to the field measured LAI data.