Synergistic algorithm for estimating vegetation canopy leaf area index andfraction of absorbed photosynthetically active radiation from MODIS and MISR data

A synergistic algorithm for producing global leaf area index and fraction o f absorbed photosynthetically active radiation fields from canopy reflectan ce data measured by MODIS (moderate resolution imaging spectroradiometer) a nd MISR (multiangle imaging spectroradiometer) instruments aboard the EOS-A M I platform is described here. The proposed algorithm is based on a three- dimensional formulation of the radiative transfer process in vegetation can opies. It allows the use of information provided by MODIS (single angle and up to 7 shortwave spectral bands) and MISR (nine angles and four shortwave spectral bands) instruments within one algorithm. By accounting features s pecific to the problem of radiative transfer in plant canopies, powerful te chniques developed in reactor theory and atmospheric physics are adapted to split a complicated three-dimensional radiative transfer problem into two independent, simpler subproblems, the solutions of which are stored in the form of a look-up table. The theoretical background required for the design of the synergistic algorithm is discussed.