An optimized broad-band leaf chlorophyll estimator

A comparison of the sensitivity of several broad-band and narrow-band vegetation indices (VI) to leaf chlorophyll concentration is conduced by the analysis of a large synthetic dataset obtained by using in the direct mode the coupled PROSPECT+SAILH leaf and canopy reflectance models. The newly proposed broad-band OCVI (Optimized Chlorophyll Vegetation Index) outperformed as a leaf chlorophyll estimator at the canopy scale both broad-band (i.e., Green NDVI, Green Simple Ratio) and narrow-band VI (i.e.: TCARI - Transformed Chlorophyll Absorption in Reflectance Index, TCARI/OSAVI ratio - TCARI/Optimized Soil Adjusted VI - and REIP, Red Edge Inflection Position), specifically proposed as leaf chlorophyll estimators, with the exception of the TCARI/OSAVI ratio for some soil/solar elevation conditions. Changes in sensitivity of a VI over the range of chlorophyll concentration are analysed, in addition to traditional regression-based statistics, by using a sensitivity function obtained according to the method proposed by Ji and Peters (2007).