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 scanning polarimetric Doppler 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 only on the part of the Doppler spectrum with the highest signal-to-noise ratio to retrieve the shape and orientation of the dominant hydrometeor types within stratiform clouds. With the extended technique, referred to as the spectrally resolved approach, the section of the Doppler spectrum containing valid data points exceeding the noise level is analyzed by dividing it into five equally spaced parts. This allows us to retrieve up to five distinct velocity-segregated hydrometeor types. The technique utilizes range–height indicator (RHI) scans (ranging from 30 to 90° elevation) of the Doppler spectra of differential reflectivity (ZDR) and correlation coefficient (RHV) from a polarimetric Ka-band cloud radar. 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.