The Degree of Common Orientation of Hydrometeors Observed by Polarization Diversity Radars

Abstract

Measurements are presented of the extent to which a common alignment of hydrometeors exists in various forms of precipitation. The observations, obtained with circularly-polarized radars situated at Penhold, Alberta and Ottawa, Ontario, were made at wavelengths of 10.4 and 1.82 cm respectively. Good agreement between results obtained at these two wavelengths was found for observations made on similar classes of precipitation. The degree of preferred alignment is high (typically 75%) in moderate or heavy rain; the presence of ice-phase hydrometeors is usually associated with a low degree of orientation. The degree of orientation, in conjunction with other parameters, is useful for the identification of the precipitation particles. Limitations on its usefulness imposed by propagation effects and by multiple scattering are discussed briefly.