Angular Aspects of Microwave Single Scattering Albedo from Tapered Vegetation Constituents

In microwave radiometry of vegetation canopies, the most important contributor to the emission is the long vegetation constituents such as tree trunks and primary branches. Their scattering pattern depends strongly on both shape and orientation. Since they are a dominant contributor to the emission, their scattering pattern must be taken into account properly when solving radiative transfer (RT) equations. A uniform dielectric cylinder model provides a simple model for a tree trunk and primary branches, which are mostly bent, not straight, and not symmetrical with respect to ground in nature. In this paper, the effect of tapering the trunk and branch diameter with height on the single scattering albedo is investigated with numerical simulations of a vertical cone and a vertical cylinder of the same height and volume. The preliminary results show that the single scattering albedo is not symmetric with respect to 90 degrees of incidence angle for those objects such as tapered vegetation components. Its implications on the zero-order RT solutions such as tau-omega model will be also discussed.