Analysis and validation of MODIS and ASTER LAI products inverted by PROSAIL

Abstract

PROSAIL model is a coupler of PROSPECT leaf optical properties and SAIL canopy reflectance models. Its usage in leaf area index inversion could help avoid the shortages of the experience model. To identify the feasibility of leaf area index (LAI) inversion and the stability of PROSAIL model used in different scales and types of remote sensing data, this paper retrieves LAI of winter wheat in Beijing based on MODIS and ASTER by using the method of PROSAIL model inversion. Firstly, to determine the input parameters of the PROSAIL model, the sensitivity of the five parameters was analyzed. These parameters include <i>chlorophyll a+b concentration, water depth, leaf mesophyll structure parameter, leaf area index, and mean leaf inclination angle</i>. Secondly, the model reproduced the spectral reflectance of the winter wheat, using the determined parameters. Then, inversion was performed to retrieve leaf area index from MODIS and ASTER, and the simulated LAI was validated with field measurements. Because of the distinct scale difference between MODIS and field measurements, ASTER was used to upscale the field measurements by aggregating area-weighted of higher-resolution LAI to acquire LAI of corresponding lower-resolution. The results indicated that there was a high correlation between leaf area index inverted by PROSAIL and actual measurements with a reasonable spatial distribution. Furthermore, it is reliable to use PROSAIL model in remote sensing data with different scales.