Modeling the Bidirectional Reflectance and Spectral Albedo of a Conifer Forest
Abstract
Analysis of aircraft imagery and ground measurements acquired for a spruce forest stand in Howland, Maine as part of the 1990 Forest Ecosystem Dynamics Multisensor Aircraft Campaign (FEDMAC), show that the Li-Strahler geometric-optical forest canopy reflectance model can estimate spectral bidirectional reflectance factors and spectral albedo with some success. In this model, the vegetated surface is treated as an assemblage of partially illuminated ow crowns of ellipsoidal shape, and through geometric-optics and Boolean set theory, the proportion of sunlit and and shadowed canopy and background is modeled as a function of view angle. Tne model is driven by ground measurements of spectral reflectance and tree crown shape, size and spacing. Atmospherically corrected multiangular radiance measurements from the Advanced Solid State Array Spectroradiometer (ASAS) fit the shape of the modeled reflectance function quite well. Integration of the reflectance function yields a spectral albedo, which, when extended to the full solar spectrum, agrees with pyranometer measurements obtained at the site.... Albedo, Hemispherical reflectance, Bidirectional reflectance, Canopy modeling, Surface reflectance modeling.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 20, 1993
- Accession Number
- ADA263570
Entities
People
- Alan H. Strahler
- Crystal B. Schaaf
Organizations
- Phillips Laboratory