In recent years there has been an explosion in the number of numerical calculations of scattering properties for ice particles. The shapes used in the computations range from pristine crystals to very large complex aggregates. The question thus arises - which scattering model should we choose for our retrievals? And on what evidence?
We report new measurements from the 2018 PICASSO field project, during which the FAAM instrumented research aircraft sampled ice particles while multiple-wavelength polarimetric radars at the Chilbolton Observatory (wavelengths ranging from 3mm up to 10cm) probed the same clouds. We use this data to directly test the fidelity of the scattering models. The radar antennas were synchronised and the scans we controlled by a tracking system fed using live position data from the aircraft, to maximise colocation. At vertical incidence (during overpasses), Doppler spectra were collected adding a further dimension to the analysis. We use this data to probe the scattering behaviour of snowflakes and link that to their physical properties.