Leaf Area Index Retrieval Using Irs Liss-iii Sensor Data and Validation of Modis Lai Product over India

This paper reports results of an experiment LRVE (Leaf Area Index Retrieval and Validation Experiment) that was conducted over agricultural areas of Central India during winter season of 2001-02, aimed at relating field measurements of LAI to space borne IRS LISS-III data, preparation of site-level LAI maps and validation of MODIS-based 1 km LAI global fields,. Measurements of fieldlevel LAI, aerosol optical thickness and water vapor were carried out on the day of LISS-III overpass. Empirical models based on site-specific LAI-vegetation index relation were developed and used to generate 23-meter resolution LAI maps for two sites (Indore and Bhopal) covering 30 km X 30 km. These LAI images were aggregated to 1km spatial resolution and used for validation of MODIS LAI product (MOD15A1). The results indicated significant positive correlation between LAI derived from LISS-III data and MODIS data, with an overestimation in the MODIS product, with RMSE of 0.92 to 1.26 for Bhopal site and 0.20 to 0.33 for Indore site. Analysis of MODIS land cover product that forms an input in MODIS LAI retrieval algorithm, indicated error in assigning land cover class over the study sites and that could be a source of error in MODIS LAI product.