ABSTRACT
The effectiveness of modeling atmospheric ice crystals of varying aspect ratios as clusters of spheres is investigated by calculation of the backscattered intensity in the millimeter-wave range by the transition matrix approach. Both single crystals and dispersions with a few choices of the orientational distribution are considered. Our calculations reproduce the features of the backscattered intensity that are due to the overall symmetry of the crystals and yield results in agreement with analogous calculations performed by other authors within the framework of the discrete dipole approximation.
ABSTRACT
Our previous theory for calculating the scattering pattern from a single aggregate of spheres deposited on a dielectric substrate is extended to deal with a dispersion of identical aggregates onto the substrate with a random distribution of their orientations. To this end the definition of the transition matrix of an aggregate is generalized to take account of the presence of the substrate; then the transformation properties under rotation of the newly defined transition matrix are used to perform analytically the required orientational averages. When the patterns calculated with this theory are compared with the calculations for a single aggregate, it can easily be seen that the features that reveal the anisotropy of the scatterers are not canceled by the averaging procedure.
ABSTRACT
The extinction spectrum from single and aggregated hemispheres whose flat faces lie on a reflecting surface is calculated, and some of the expected resonances are found to disappear for specific choices of the direction and the polarization of the incident wave. This resonance-suppressing effect is fully explained for the case of single hemispheres, whereas for the case of aggregated hemispheres the guidelines for its explanation are given.
ABSTRACT
A method for studying the scattering properties of a cluster of dielectric spheres is proposed. The vector scattering problem is handled through Debye potentials and a mathematical technique that accounts for multiple scattering effects. The scattered field as well as the scattering and absorption cross sections can be computed without any restriction of principle on the angle of incidence of light and on the radia and refractive indexes of the spheres in the cluster. The resulting expressions take on the well known form when the cluster reduces to a single sphere.
