The first 95 GHz polarimetric radar measurements obtained in an ice-crystal cloud are presented together with model computations. The radar measurements consist of the horizontal and vertical polarization reflectivity factors (ZHH and ZVV) and degrees of polarization (DPH and DPV). Simultaneous shadow image measurements of ice crystals are obtained from a 2D-C probe in a closely located wind tunnel. These images provide the size distribution and shape information for the models. The ice crystals are mainly composed of stellar and hexagonal plates. The finite difference time domain method is used for electromagnetic scattering computations. A three dimensional canting distribution is incorporated in the study. The simulated ZHH values compare very well with the radar measurements (i.e., the mean values are within 1 dB). ZVV also compares well well for a specific canting distribution as do the mean values of DPH, DPV and ZDR (differential reflectivity). It is observed that ZHH (unlike ZVV) is not very sensitive to the orientation of planar crystals, but it is sensitive to the change in their thickness. Hence, ZHH is a preferable radar measurand for estimating ice crystal mass.
All Science Journal Classification (ASJC) codes
- Atmospheric Science