Retrievals of the Deep Convective System Ice Cloud Microphysical Properties using Nexrad and Aircraft In-situ Measurements

Abstract:

This study presents a newly developed algorithm for retrieving deep convective system (DCS) ice cloud microphysical properties using Next-Generation Radar (NEXRAD) reflectivity during the Midlatitude Continental Convective Clouds Experiment (MC3E) at the Atmospheric Radiation Measurement (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 cloud radar reflectivity by heavy precipitation, unknown particle size distributions (PSDs) and the habit of the ice particles in sample volume. In this study, NEXRAD (precipitation radars) reflectivity, with no/little attenuation in heavy precipitation and intense spatial coverage, has been used in retrieval, although it has lower vertical resolution than cloud radars. The aircraft in-situ measurements observed PSDs were fit to analytic function (gamma function) to compare observations made in different meteorological conditions (stratiform rain /anvil regions of DCS) and to best reproduce the true PSD for retrievals. The aircraft in-situ cloud particle imager (CPI) measurements show the habit of the ice particles (aggregates). The relationship between backscatter cross section (σ) and particle dimension (D) is parameterized for the ice crystal habit (aggregates) with the aid of scattering database. Results of the vertical profiles of ice water content (IWC) and median mass diameter (D_m) in ice cloud of DCS, which have been retrieved from NEXRAD reflectivity assuming gamma distribution and σ-D relationship during the MC3E, will be presented. The retrieved microphysical properties are also validated by aircraft in-situ best-estimated IWC and D_m.