Estimation of vegetation canopy leaf area index and fraction of absorbed photosynthetically active radiation from atmosphere-corrected MISR data

The multiangle imaging spectroradiometer (MISR) instrument is designed to p rovide global imagery at nine discrete viewing angles and four visible/near -infrared spectral bands. This paper describes an algorithm for the retriev al of leaf area index (LAI) and fraction of photosynthetically active radia tion absorbed by vegetation (FPAR) from atmospherically corrected MISR data . The proposed algorithm is designed to utilize all the information provide d by this instrument, using a two-step process. The first step involves a c omparison of the retrieved spectral hemispherically integrated reflectances with those determined from the model which depend on biome type, canopy st ructure, and soil/understory reflectances. The biome/canopy/soil/understory models that pass this comparison test are subject to the second step, whic h is a comparison of their directional reflectances at the MISR angles to t he retrieved spectral directional reflectances. This procedure, however, ca n produce multiple acceptable solutions. The measure theory is used to spec ify the most probable values of LAI and FPAR using the set of all acceptabl e solutions. Optimization of the retrieval technique for efficient global p rocessing is discussed. This paper is the second of a two-part set describi ng a synergistic algorithm for producing global LAI and FPAR fields from ca nopy reflectance data provided by the MODIS (moderate resolution imaging sp ectroradiometer) and MISR instruments.