Estimation of the effective ice content on Earth-satellite paths from dual-polarisation measurements at Ka-band

The paper presents a technique to estimate the instantaneous effective ice content (IC) in clouds from measurements of the differential propagation characteristics of the Earth-satellite transmission channel. High concentrations of ice crystals possessing a significant degree of common orientation have their habitat near the top of some types of clouds. They can induce important degradation of the crosspolar discrimination (XPD) on Earth-satellite links. The ice content is a fundamental parameter of models designed to compute XPD due to atmospheric ice crystals, and to the authors´ knowledge, time series of the IC have not yet been published. As a part of the technique for estimating the IC, a procedure for separating the contributions of rain and ice to depolarisation is proposed. The results obtained by applying the technique to data recorded during the Olympus satellite propagation campaign are presented. The estimates are in good agreement with values derived from radar measurements. Finally, the values of IC retrieved from recordings at 20 GHz are used to simulate XPD at 12.5 GHz. Resulting in very good agreement with measurements.