Polarimetric properties of ice cloud particles

Polarimetric radar observations in clouds above the melting layer could be helpful in understanding of the processes of particles' formation and generation of precipitation. Ice cloud particles have variety of forms: from simple plates and needles to multy branch dendrites, stars, and aggregates. A method to calculate radar polarimetric properties of fancy shaped ice particles is described. The method is based on the representation of a complex particle as a collection of particles of simple shapes. The polarimetric properties of the collection are calculated as a coherent sum of polarimetric properties of simple-shape scatterers by taking into consideration their relative locations and orientations. The method can be applied to a wide range of mm and cm wavelengths because of low value of dielectric permittivity of ice.

The method is applied to radar data. It is shown that measurements of differential reflectivity and copolar correlation coefficients can be used to distinguish two large categories of shapes: needle-like and plate-like ones. Cloud areas containing plate/dendrite-shaped and needle-like particles are demonstrated in radar data collected at X and S bands.