Accession Number : ADA289668

Title :   Modeling Directional Thermal Radiance from a Forest Canopy.

Corporate Author : NEW HAMPSHIRE UNIV DURHAM

Personal Author(s) : McGuire, Mark J. ; Balick, Lee K. ; Smith, James A. ; Hutchinson, B. A.

PDF Url : ADA289668

Report Date : 1989

Pagination or Media Count : 22

Abstract : 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. (AN)

Descriptors :   *THERMAL RADIATION, *FORESTS, *TREE CANOPY, HEAT TRANSFER, MATHEMATICAL MODELS, DATA PROCESSING, ANGLES, POSITION(LOCATION), PREDICTIONS, COMPARISON, SURFACE ROUGHNESS, MONTE CARLO METHOD, VARIATIONS, PROFILES, THERMAL ANALYSIS, GEOMETRIC FORMS, VEGETATION, AZIMUTH, HEIGHT, SOLAR HEATING, THERMAL IMAGES, SUN, FOURIER SERIES.

Subject Categories : Forestry
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE