Scaling effect on the estimation of chlorophyll content using narrow band NDVIs based on radiative transfer model

The aim of this work is to compare the estimations of chlorophyll contents at foliar level and canopy level by using narrow band normalized difference vegetation indices. The canopy spectra reflectance and foliar spectra reflectance used in this work are simulated under different chlorophyll contents based on PROSPECT model and SAIL model. 10 narrow band NDVIs were selected at the identified ranges that can effectively assess foliar chlorophyll content. Firstly, we calculated the correlations between leaf chlorophyll contents and narrow band NDVIs and pick up ten optimal narrow band NDVIs that can assess leaf chlorophyll contents. Then, these ten narrow band NDVIs were applied to estimate chlorophyll contents at canopy level. The adaptation of the ten narrow band NDVIs used in assessing the canopy chlorophyll content were evaluated finally. As for each narrow band NDVI, we analyzed the correlation with the canopy chlorophyll content and the sensitivities to all canopy parameters. As a result, we found that only two narrow band NDVIs (i.e., NDVI(875, 725) and NDVI(900,720)) can be applied for the estimation of chlorophyll contents at canopy level.