Microwave and submillimeter wave scattering of oriented ice particles

Abstract

Abstract. Microwave dual-polarization measurements above 100 GHz are so far sparse, but they consistently show that larger ice hydrometeors tend to deviate from the standard assumption of total random orientation. This conclusion has been derived by conceptual models, while the first detailed simulations, recreating the observed polarization patterns, are presented in this study. The ice particles are assumed to be azimuthally randomly oriented with a fixed but arbitrary tilt angle. The scattering data for azimuthal random orientation is much more complex than for total random orientation. The scattering data of azimuthally randomly oriented particles depends in general on the incidence angle and two scattering angles compared to one angle scattering for total random orientation. The additional tilt angle adds an additional dimension. The simulations are based on the discrete dipol approximation in combination with a self developed orientation averaging approach. Data for two particle habits (51 hexagonal plates and 18 plate aggregates) and 35 frequencies between 1 GHz and 864 GHz were produced. The data is publicly available from Zenodo (https://doi.org/10.5281/zenodo.3463003). This effort is also an essential part of preparing for the upcoming Ice Cloud Imager (ICI), that will perform polarized observations at 243 GHz and 664 GHz, which will deliver new insights about clouds.