Numerical Evaluation of Radiation Extinction Coefficient Using Fractal Geometry for Vegetation Modeling

This article focuses on the accurate determination of the radiation extinction coefficient (β) for a vegetal set like a tree in the frame of forest fires. Usually, this coefficient is calculated using the De Mestre relationship, not taking into account the leaf orientation and position. In order to evaluate their role, a realistic vegetal structure is numerically created using LAI data, De Wit's models, and IFS geometry. A ray-tracing method is used to simulate the radiative transfer inside the numerical tree. The results show that the leaf distribution and position cannot be neglected in β determination. The use of well-known correlations are not sufficient to predict β: over-estimations of up to 100% have been observed.