Influence of atmospheric correction on the estimation of biophysical parameters of crop canopy using satellite remote sensing

A quantitative approach has been made for the estimation of biophysical par ameters of a vegetation canopy by the inversion of a vegetation canopy refl ectance model. Model inversion has been done using a non-linear optimizatio n scheme against directional reflectance data over the canopy. A quasi-Newt on algorithm has been employed that searches the minimum of a function iter atively using the functional values only. The technique provides a reasonab ly good estimation of the biophysical parameters. A study has been conducte d to quantify the error related to the estimation of biophysical parameters of vegetation with simulated satellite data corrected with improper values of atmospheric aerosol and water vapour contents. In the visible, atmosphe ric correction of satellite data with improper values of atmospheric aeroso l content results in a modification of the amplitude and angular pattern of the directional reflectance for both low-density and high-density vegetati on canopies. However, in the near-infrared, the atmospheric correction of d ata with improper values of aerosol and water vapour contents changes the a mplitude of directional reflectance, but, no significant changes in angular pattern are noticed. This study indicates that parameter estimation can be significantly influenced by using improper values of both aerosol and wate r vapour contents during data correction in the visible and near-infrared r egions of the solar spectrum. The estimation accuracy is higher for a low-d ensity canopy than for a dense vegetation canopy. Retrievals of all the sur face parameters are not equally affected by such improper atmospheric corre ction of data. Particularly, estimations of soil reflectance and leaf area index are significantly influenced by such improper correction for a high-d ensity vegetation canopy. However, the accuracy of the retrieved parameter values is higher in the near-infrared than in the visible for both high-den sity and low-density canopies.