Analysis of polarization radar returns from ice clouds

Using a modified T-matrix code, some polarimetric single-scattering radar parameters (Zh,v, LDRh,v, ρhv, ZDR and δhv) from populations of ice crystals in ice phase at 94 GHz, modeled with axisymmetric prolate and oblate spheroidal shapes for a -size distribution with different α parameter (α = 0, 1, 2) and characteristic dimension Lm varying from 0.1 to 1.8 mm, have been computed. Some of the results for different radar elevation angles and different orientation distribution for fixed water content are shown. Deeper analysis has been carried out for pure extensive radar polarimetric variables; all of them are strongly dependent on the shapes (characterised by the aspect ratio), the canting angle and the radar elevation angle. Quantities like ZDR or δhv at side incidence or LDRh and ρhv at vertical incidence can be used to investigate the preferred orientation of the particles and, in some cases, their habits. We analyze scatterplots using couples of pure extensive variables. The scatterplots with the most evident clustering properties for the different habits seem to be those in the (ZDR [X = 0°], δhv [X = 0°]), in the (ZDR [X = 0°], LDRh [X = 90°]) and in the (ZDR [X = 0°], ρhv [X = 90°]) plane. Among these, the most appealing one seems to be that involving ZDR and ρhv variables. To avoid the problem of having simultaneous measurements with a side and a vertical-looking radar, we believe that measurements of these two extensive variables using a radar with an elevation angle around 45° can be an effective instrument to identify different habits. In particular, this general idea can be useful for future spaceborne polarimetric radars involved in the studies of high ice clouds. It is also believed that these results can be used in next challenge of developing probabilistic and expert methods for identifying hydrometeor types by W-band radars. © 2001 Elsevier Science B.V. All rights reserved.