Single-scattering properties of droxtals

Small ice crystals have been found to occur in high concentrations in polar stratospheric clouds and the upper portion of cirrus clouds, where temperatures are extremely low (often less than -50°C). The scattering properties of these small crystals are important to space-borne remote sensing, especially for the retrieval of cirrus properties using visible and near-infrared channels. Previous research has shown that the commonly used spherical and "quasi-spherical" approximations for these ice crystals can lead to significant errors in light scattering and radiative transfer calculations. We suggest that droxtals more accurately represent the shape of these small ice crystals. The single-scattering properties of ice droxtals have been computed at visible and infrared wavelengths using the finite-difference time domain method for size parameters smaller than 20. Further study of the optical properties of larger droxtals (size parameter greater than 20) will be carried out using an improved geometric optics method.