Modeling directional thermal radiance from a forest canopy
This paper describes an extension of an existing thermal vegetation canopy radiance model which has been modified to partially account for the geometrically rough structure of a forest canopy. Fourier series expansion of a canopy height profile is used to calculate view factors which partially account for the directional variations in canopy thermal radiance transfer. A modification of a previously developed thermal vegetation canopy model is presented, along with the measurements used to drive and verify the model. The evidence indicates that thermal radiance from a forest canopy depends on sensor viewing angle, solar position, and the degree of geometric roughness of the canopy surface. For the above canopy, hand-held IRT`s were not useful for investigating the nadir angle variations due to the averaging technique used. These data did show some azimuthal variations, but it is difficult to precisely interpret the trends because of the averaging employed. Comparisons were made between the ORIG and ROUGH thermal models. The data analysis and model comparisons suggest that thermal radiance from a forest canopy does depend on sensor view angle and that the variation can be partially explained by the position of the sun and the geometrically rough structure of the canopy surface.
- Research Organization:
- New Hampshire Univ., Durham, NH (United States)
- OSTI ID:
- 91747
- Report Number(s):
- AD-A-289668/6/XAB; TRN: 52120515
- Resource Relation:
- Other Information: PBD: 1989
- Country of Publication:
- United States
- Language:
- English
Similar Records
Geometric-optics forest canopy modelling for high spatial resolution imagery
Evaluating the functionality and streamflow impacts of explicitly modelling forest-snow interactions and canopy gaps in a distributed hydrologic model