Ice Microphysical Retrievals Using W-band Airborne Radar Polarimetric Observations

The polarimetric radar backscatter measurements of cloud particles depend on their microphysical properties (size, shape, concentration, fall pattern, density and phase). The non-spherical geometry (aspect ratio), density, and size of ice crystals provide valuable information for identifying various ice habits and enable retrievals of microphysical properties from radar polarimetric measurements. Newly developed polarimetric retrievals demonstrate considerable potential in qualitatively estimating ice water content (IWC), total number concentration (Nt), and mean volume diameter (Dm) of ice particles. These retrievals were found to be more accurate than non-polarimetric methods in terms of correlation with in situ measurements and estimation bias. While polarimetric retrievals using centimetre-wavelength radar have been demonstrated and evaluated in recent works, the use of millimetre-wavelength radar observations for retrievals is not yet widely adopted.

In this paper, we will evaluate the effectiveness of polarimetric retrievals for ice clouds using W-band airborne radar and in situ data collected during the Winter Precipitation Type Research Multi-Scale Experiment (WINTRE-MIX) campaign conducted in winter 2022. The coincident, co-located, and high-resolution airborne data provide an excellent means of developing, improving, and validating radar retrieval algorithms while minimizing the temporal and spatial volume mismatch between radar and in-situ measurements. Specifically, this analysis utilizes radar data obtained from a side-looking antenna and from a down-forward looking antenna with a sufficiently high incidence angle. The cloud particle size distribution was determined using a combination of data from several single particle probes, while the total water content (TWC) and liquid water content (LWC) were measured using the Nevzorov probe.