Measurements of ice depolarization at 28.56 GHz using the COMSTAR Beacon simultaneously with a 16.5 GHz polarization diversity radar

Measurements on ice depolarization made at the National Research Council in Ottawa, using a 16.5-GHz polarization diversity radar concurrently with the 28.56-GHz COMSTAR beacon, are reported. The radar, which is normally operated in a circular polarization mode, provides data on polarization parameters such as the cancellation ratio and the degree of preferred orientation. Frequently, the differential propagation parameters can be determined. From these data, identification of different kinds of hydrometeors (i.e., rain, melting layer, and ice crystals) along the path is possible. The beacon receiver measures the differential attenuation and the differential phase shift between two linear orthogonal components of the received signal, and the copolar attenuation. Several occurrences of ice depolarization in the presence of rain were observed. From radar data, identification of the hydrometeors was made and the contribution of each type toward the differential propagation parameters was determined. Good agreement between radar and beacon receiver measurements was obtained. Also several events of ice depolarization in the absence of rain are reported. The results presented here provide new data on ice depolarization and demonstrate the usefulness of simultaneous polarization diversity radar and beacon measurements for obtaining a better understanding of the nature of ice depolarization. Because of the limited observation period, emphasis is given to the nature of the phenomenon rather than to the statistics of its occurrence.