Comparison of MODIS LAI Data Products in Mclean County, Illinois.

In 2000, shortly after NASA Terra was launched, Dr. Doraiswamy started experiments to determine the usefulness of the Moderate Resolution Imaging Spectroradiometer (MODIS) for crop modeling, particularly the Leaf Area Index (LAI) data product (MOD15A).  The field experiments were conducted in Mclean County, Illinois during the 2000 crop season.  LAI, crop reflectance and other crop growth parameters were measured in 16 fields of corn and soybeans at least 4 times over the growing season, and were used to calibrate a canopy radiative transfer model for the MODIS 250-m red and near-infrared bands.   LAI was calculated from the radiative transfer model and was compared to the MODIS LAI data product.  The MODIS LAI data product (both versions 3 and 4) had significant errors, so the MODIS 250-m data were used directly as inputs for crop models.  Since then, version 5 has been released and historical MODIS data were reanalyzed by NASA.  The values from the current MODIS LAI data product were in agreement with the measured data from 2000.  Thus, the value of the LAI data product for input to crop models needs to be reassessed.