P2.67 Retrieval of Microphysical Properties of Snow Using Spectral Dual Polarization Analysis

Snow crystals consist of many different types of ice particles. Typical radar measurements observe only bulk properties of all types of ice particles present in a radar volume. Due to their difference in cross-section, large particles will reflect more power of the transmitted radar signal than small particles. If small and large particles are present in the same radar volume with comparable volume concentrations, the radar measurements will be dominated by larger particles. Because of this, it is difficult to obtain microphysical properties of both large and small particle types, based on reflectivity alone. In this work, application of spectral dual polarization analysis for retrieval of microphysical properties of ice particles in stratiform precipitation is presented. Based on literature research a selection on the particle types that are predominantly present in radar measurements is done. The selection is based on radar crosssections of the different particles and on meteorological conditions as well. The radar cross-sections are calculated with a model derived from literature. With the obtained knowledge, it is shown that only aggregates and plates dominate spectral radar retrievals above the melting layer of stratiform precipitation. A model is created to simulate spectral radar observables of plates and aggregates. This model is dependent on the parameters of the drop size distribution of plates and aggregates, ambient wind velocity and spectral broadening. The simulated radar spectra are fitted to radar measurements using a non-linear least squares optimization technique. The data is obtained at the measurement site Cabauw, The Netherlands by TARA (Transportable Atmospheric Radar)