Identification of multiple co-located hydrometeor types in Doppler spectra from scanning polarimetric cloud radar observations

Abstract. To date, there remains a noticeable gap in reliable techniques for retrieving the shape and orientation of ice particles from observational data. This paper introduces a method using ground-based polarimetric cloud radar to retrieve the shape and orientation of multiple hydrometeor types within deep mixed-phase clouds. Building on the strong performance of an existing method, which is effective in retrieving the shape and orientation of pristine ice particles in stratiform clouds, we extended this technique by analyzing the entire Doppler spectrum. The previously developed main-peak approach focuses on the maximum of the Doppler spectrum to retrieve the shape and orientation of the dominant hydrometeor types within stratiform clouds. In the extended technique, referred to as the spectrally resolved technique, the full Doppler spectrum is analyzed by dividing it into five parts, ultimately allowing the retrieval of five distinct hydrometeor types. In this study, we employed the technique for Range-Height Indicator (RHI) scans (ranging from 30° to 90° elevation) utilizing polarimetric Ka-band cloud radar observations of differential reflectivity (ZDR) and correlation coefficient (RHV) across the entire Doppler spectrum. The potential of the improved approach is presented by means of two case studies. The first case demonstrates the effectiveness of the spectrally resolved approach and in the second case secondary ice production is investigated. These findings contribute to a profound understanding of hydrometeor characteristics, shedding light on dynamic cloud processes, especially in the context of precipitation and ice particle formation.