Absorption profiles of shortwave radiation in a vegetation canopy
Agricultural and Forest Meteorology 62(3-4): 191-204
ISSN/ISBN: 0168-1923 DOI: 10.1016/0168-1923(92)90014-u
Absorption profiles of incoming solar radiation determine incoming fluxes between vegetation-covered ground and the atmosphere. On the basis of the Nilson-Kuusk canopy reflectance model a procedure for calculating the absorption profiles inside a homogeneous vegetation canopy is proposed. The model considers the absorption of uncollided and single-scattered radiation including specular reflection on leaves and the hot-spot effect. Multiple scattering is considered in a two-stream approach. Model calculations demonstrate significant deviations of absorption profiles from an exponential distribution in the near-IR spectral region and high dependence of profiles on foliage orientation and the solar zenith angle. The set of input parameters of the model coincides with that of the Nilson-Kuusk canopy reflectance model. These parameters can be estimated from remote measurements of the angular distribution of canopy directional reflectance.