Light Scattering Properties of Higher Order Chebyshev Particles and Implications for Aerosols with a Weak Surface Roughness

Kurzfassung

Chebyshev particles of comparatively low orders n are used in the past to study the effects of nonspherical but concave geometries in remote sensing applications. Their shape is given by r(theta) = r0 * [1 + a * cos(n * theta)] where r0 is the radius of the underlying sphere and a denotes the deformation parameter. We present results of light scattering computations for several Chebyshev particles characterized by higher orders n. Accurate results can be obtained for such particles within a T matrix approach. Moreover the scattering characteristics converge to stable results if the order is increased. Essential differences between, e.g., the phase functions of the higher order Chebyshev particles and the underlying regular scatterers can be observed. In particular an increased backscattering due to the surface roughness is obtained. This behavior is even more pronounced in the case of highly absorbing particles. The effects obtained agree with results of other approaches and correspond to expectations for particles with a weak surface roughness. This demonstrates that, on one hand, higher order Chebyshev particles can be used to estimate the influence of a weak surface roughness on the light scattering behavior of atmospheric aerosols. On the other hand, the consideration of roughness effects is important in the retrieval of aerosol properties.