ALBERT

Description: The single scattering properties of nonspherical raindrops have been calculated by means of the geometric optics approximation to ascertain the usefulness of lidar remote sensing of rainrates. Based on the theoretical hydrodynamical studies of Chuang and Beard (J. Atmos. Sci., 1990, 47, 1374Ð1389), a Chebyshe¤-series of shape coe¦cients has been selected to account for the size dependent particle nonsphericity. The single scattering calculations for randomly oriented raindrops with particle radii ranging from 0.5 to 4.5mm exhibit a very pronounced dependence of the phase matrix on particle shape. However, most of these changes are not monotonic with increasing size, which complicates correlations between rainrates and the radiative properties of the raindrops. A comparison of ray tracing results by Chebyshe¤-type particles and axis-ratio equivalent spheroids shows signiÞcant di¤erences for particles with radii larger than 1 mm. Backscattering intensity as well as linear and circular depolarization ratios for horizontally oriented raindrops show a non-monotonic increase with particle size. The size distribution averaged backscattering properties are poorly correlated with rainrates. We conclude that lidar remote sensing of rainrates does not seem to be a promising attempt. However, this conclusion may be subject to changes if raindrop oscillations, which have not been considered in this study, a¤ect the size distribution averaged backscattering properties.