Retrievals of the deep convective system ice cloud microphysical properties using the ARM radar and aircraft in - situ measurements

This paper presents a newly developed algorithm for retrieving ice cloud microphysical properties in deep convective system (DCS) using ARM Ka-band cloud radar (KAZR) reflectivity during the Midlatitude Continental Convective Clouds Experiment (MC3E) at the ARM Southern Great Plain (SGP) site during April-June 2011. The fundamental problems to retrieve the ice cloud microphysical properties of DCS using radar reflectivity are the attenuation of KAZR reflectivity by either heavy precipitation or large liquid water paths, unknown particle size distributions (PSDs) and the habit of the ice particles in sample volume. In this study, the attenuated KAZR reflectivity measurements have been corrected through a novel approach combining UAZR, KAZR, and disdrometer data. The aircraft in-situ measurements provide the best-estimate ice water content (IWC), PSDs, and a modified gamma function for validating the radar retrievals. With the aid of scattering database (SCATDB), the relationships between backscatter cross section (σ)and particle dimension (D) are parameterized for four ice crystal habits (bullet rosettes, snowflakes, column and plates). The ice cloud IWC and effective radius (re) on the case of 20 May 2011 during the MC3E have been retrieved from corrected KAZR reflectivity assuming a modified gamma distribution, size shape α=2.0 and a bullet rosette σ-D relationship. The averaged IWC and re from radar retrievals over the ice-phase layer of DCS are 0.32 g m-3 and 320 µm, having an excellent agreement with aircraft in-situ measured IWC (0.34 g m-3) and re (337 µm). Over the Anvil region, the retrieved and measured IWCs are 0.14 g m-3 and 0.23 g m-3, and their re values are 220 µm and 305 µm. Comparing the aircraft in-situ measurements, the uncertainties for radar-retrieved re and IWC are about 5% over the ice-phase layer of DCS, while they are approximately 30% over the Anvil region of DCS from this case study. More cases are needed to further validate the radar retrievals in the future.