Ice microphysics from multifrequency suites of active and passive remote sensing instruments

• Main Author: Kalogeras, Petros
• Format: Dissertation
• Language: English
• Published: University of Leicester 2021
• Subjects: Ice microphysics; multifrequency suites; remote sensing; thesis
• DOI: 10.25392/leicester.data.19070243.v1

High-latitude processes and polar cloud microphysics envelop research areas the furtherance of which in the more accurate description of the arctic energy budget, climate variability, and feedbacks is essential. This study develops and assesses a multifrequency and Doppler-inclusive, ice particle size distribution retrieval technique for mean mass-weighted diameter and ice water content, and additionally proposes a radaronly, moment-based phase partition scheme tailored to polar regions. The technique is applied to datasets collected by the ARM research facility at the North Slope of Alaska and two ARM Mobile Facility 2 campaigns (BAECC, AWARE) that comprise a gamut of ground-based profiling sensors including radars at X, Ka, and W bands, lidar, and microwave radiometer. The microphysical retrieval is a multi-instrument task; firstly, a Ka-band -based, reflectivity-velocity power-law scheme estimates an ice sedimentation velocity corrected for the vertical wind component. An attenuation correction is then applied for the estimation of effective reflectivities. Both reflectivity and sedimentation velocity are integrated in a Bayesian scheme that compares observations against lookup- tables in both backscattering and hydrodynamic ice-particle properties. The radar only, phase partitioning is proven reliable in detecting cloud-top supercooled liquid water layers. Aggregate statistics are computed based on BAECC data. The combined utilization of radar reflectivity in a dual- or triple-frequency forward modeling in conjunction with sedimentation velocity, demonstrates that Doppler observations can assist in microphysical characterizations because connections across observations and simulations of both ice scattering and hydrodynamic properties are less ambiguous compared to scattering-only. Results demonstrate less retrieval spread among X / Ka / W / Doppler or Ka / W / Doppler retrieval scenarios as opposed to X / Ka / W. Lastly, the inclusion of a lower frequency (10-15 GHz) is advocated due to its significance in signal mitigation (attenuation, cross-calibration) and in the retrieval forward modeling ambiguity constraining.