HR: 0800h
AN: B21A-0027    [Abstracts]
TI: Partitioning incident radiation fluxes based on photon recollision probability in vegetation canopies
AU: * M~ottus, M
EM: mottus@ut.ee
AF: Tartu Observatory, T~oravere, Tartumaa, 61602, Estonia
AU: * M~ottus, M
EM: mottus@ut.ee
AF: University of Helsinki, Department of Forest Resource Management, P.O. Box 27, Helsinki, 00014, Finland
AU: Stenberg, P
EM: pauline.stenberg@helsinki.fi
AF: University of Helsinki, Department of Forest Resource Management, P.O. Box 27, Helsinki, 00014, Finland
AB: Remote sensing of vegetation and modeling of canopy microclimate requires information on the fractions of incident radiation reflected, transmitted and absorbed by a plant canopy. The photon recollision probability p allows to calculate easily the amount of radiation absorbed by a vegetation canopy and to predict the spectral behavior of canopy scattering, i.e. the sum of canopy reflectance and transmittance. However, to divide the scattered radiation into reflected and transmitted fluxes, additional models are needed. To overcome this problem, we present a simple formula based on the photon recollision probability p to estimate the fraction of radiation scattered upwards by a canopy. The new semi-empirical method is tested with Monte Carlo simulations. A comparison with the analytical solution of the two-stream equation of radiative transfer in vegetation canopies is also provided. Our results indicate that the method is accurate for low to moderate leaf area index (LAI) values, and provides a reasonable approximation even at LAI=8. Finally, we present a new method to compute p using numerical radiative transfer models.
DE: 0416 Biogeophysics
DE: 0466 Modeling
DE: 0480 Remote sensing
SC: Biogeosciences [B]
MN: 2007 Fall Meeting