Synergy between 1-D and 3-D radiation transfer models to retrieve vegetation canopy properties from remote sensing data

B. Pinty, N. Gobron, J.-L. Widlowski, T. Lavergne, M. M. Verstraete
2004 Journal of Geophysical Research  
1] We devise a computer efficient and flexible inversion technique to retrieve vegetation canopy parameters, in particular the Leaf Area Index, from the radiance field emerging at the top of a structurally heterogeneous systems overlying an anisotropic spatially uniform surface background. The proposed inversion strategy focuses on a reanalysis of multiangle and multispectral measurements unhindered by the many specific constraints imposed by the operational application of the current
more » ... and their associated limitations on data staging. This technique capitalizes on the decoupling between contributions due to the canopy only and those invoking the background reflectance properties. These contributions are decomposed into the wavelength dependent and independent contributions. A quasi-linear relationship is thus obtained between the radiance/reflectance emerging from the top of the canopy layer and the background reflectance. Although all individual contributions can be estimated from accurate three-dimensional radiation transfer models, we propose appropriate approximations in order to estimate the minor terms. These approximations exploit the relatively limited dependency exhibited by these relatively smaller contributions with respect to the azimuthal coordinate. Moreover, additional mathematical developments are proposed to further approximate these terms by their corresponding solutions obtained in the limit case of a plane-parallel turbid medium scenario. They require defining effective values of the state variables entering the plane-parallel turbid medium model. The resulting reflectance of a three-dimensional spatially heterogeneous vegetation layer is driven by a sum of contributions that can be precomputed offline on the basis of the three-dimensional and plane-parallel homogeneous turbid medium model capabilities. The decoupling of the intrinsic vegetation and the background contributions allows many of the contributions to be precomputed and stored in look-up tables. This development yields a simple and computer efficient inversion scheme that allows us to jointly retrieve the values of the main vegetation layer attributes and the underlying background radiative properties. Demonstration tests based on actual multiangular and multispectral data set are currently being investigated. Citation: Pinty, B., N. Gobron, J.-L. Widlowski, T. Lavergne, and M. M. Verstraete (2004), Synergy between 1-D and 3-D radiation transfer models to retrieve vegetation canopy properties from remote sensing data,
doi:10.1029/2004jd005214 fatcat:6uutthycbjahvaxzhu32vyxzaa