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Simulation of the effect of snow covered forest floor on the total forest albedo

Author(s): Manninen T, Stenberg P

Published: February, 2009

Publisher: Agricultural and Forest Meteorology

DOI: 10.1016/j.agrformet.2008.08.016

Tags: Afforestation

URL: http://www.sciencedirect.com/science/article/pii/S0168192308002414

Abstract: An existing forest reflectance model based on photon recollision probability is extended to be applicable also in the case of snow covered forest floors. In summer conditions (small forest floor albedo), as is normally assumed, the part of the total forest albedo originating from the forest floor is mainly from bidirectional transmission through gaps in the canopy (photons transmitted without interaction through the canopy first downwards and then upwards after being reflected at the forest floor). The extended model developed in this paper additionally takes into account multiple scattered photons, which have interacted within the canopy prior to or/and after being reflected by the forest floor. The bidirectional reflectance distribution function (BRDF) of the forest floor is assumed to be a mixture of a Lambertian and a purely forward/backward scattering surface. Results show that snow covered forest floors affect the total canopy albedo to a large extent via this multiple scattered component included in the model. If it is not taken into account the canopy albedo estimate may be up to 0.2 units too small. Lambertian and purely forward/backscattering forest floors cause practically similar total forest albedo values for moderate sun zenith angle values. The black and white sky albedo values are very similar. The developed albedo model was successfully used to simulate the main features of measured albedo values.


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