LAI estimation by means of the WDVI: A sensitivity analysis with a combined PROSPECT‐SAIL model

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Abstract
The PROSPECT leaf reflectance model and the SAIL canopy reflectance model were combined for quantifying the accuracy of LAI estimation from the Weighted Difference Vegetation Index (WDVI). The WDVI was developed as part of the CLAIR model for correcting the near‐infrared reflectance for soil background. From the PROSPECT‐SAIL simulations, it is concluded that the influence of external factors, such as soil reflectance, ratio diffuse/total irradiation and solar‐view geometry, will not pose a large problem for the relationship between LAI and WDVI. Moreover, leaf variables such as leaf chlorophyll content, leaf mesophyll structure and hot spot size‐parameter have quite a small influence for green leaves at near‐nadir observations (e.g. Landsat and SPOT‐nadir). The main variable influencing the relationship between WDVI and LAI is the leaf inclination angle distribution.