ORCID

https://orcid.org/0000-0003-2570-6037

Date of Award

Summer 2025

Language

English

Embargo Period

7-11-2027

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Electrical and Computer Engineering

Program

Electrical and Computer Engineering

First Advisor

Dr. Mustafa Aksoy

Committee Members

Dr. Mustafa Aksoy, Dr. James R. Moulic, Dr. Gary J. Saulnier, Dr. Thomas R. Hanley

Keywords

Microwave Radiometry, Remote Sensing, Antarctic Firn, Cryosphere, Global Precipitation Measurement, Ice sheets

Subject Categories

Climate | Electrical and Electronics | Electromagnetics and Photonics | Glaciology | Other Earth Sciences | Other Electrical and Computer Engineering

Abstract

Climate Change is a widely known global phenomenon referring to long-term shifts in temperature and weather patterns which have had a deep impact on the Earth’s cryosphere. So, understanding the behavior of the cryosphere is essential for predicting future changes in the polar firn coverage which are critical to characterize the weather, climate, and the water cycle of the Earth. These are the distant parts of the world where meteorological research stations have been set up, but remote sensing is the most prevalent way for collecting any measurements due to extremely harsh environmental conditions associated with these regions along with being very challenging and costly to get in-situ measurements. In this research satellite-based microwave radiometry is used since it is highly sensitive to the physical and thermal properties of the polar firn and provides data from the cryospheric regions of the Earth irrespective of solar illumination and cloud conditions. Different frequencies within the wide spectrum of microwave radiometers result in different electromagnetic propagation losses and thereby reveal characteristics at different depths in the firn. Previous attempts have been made where microwave radiometers have been developed over a narrow frequency range and deployed to retrieve internal temperature profiles from the deep ice over the Greenland Ice sheets. This research work expanding on those analyses, explores the utilization of Global Precipitation Measurement (GPM) constellation as a single wideband (6.9 GHz -91.655 GHz) spaceborne radiometer covering the microwave spectrum from C-Band to W-band, to profile the subsurface properties of the Antarctic firn. To start with, initial investigations have been conducted over the Concordia and Vostok stations in Antarctica which reveal that GPM brightness temperatures can provide critical information regarding subsurface temperatures and physical properties of the firn from the near surface to several meters of depth. The overarching goal of this research is thereby the complete characterization of the Antarctic firn layers in terms of its thickness, density, grain size and physical temperature through multi-frequency wideband passive microwave remote sensing. To start, archived in-situ measurements of the Antarctic firn density, grain size and internal temperature are collected along with the recent GPM constellation measurements. A forward electromagnetic emission model is developed, and the simulated results are compared to the v GPM constellation measurements to evaluate and improve the state-of-the-art forward microwave emission models. After this, using the GPM measurements, the physical temperature, density, and grain size parameters of the Antarctic firn layers are estimated with respect to depth through retrieval algorithms based on a lookup table method and built on the improved forward emission model. Furthermore, validation of the results is conducted with scopes for future possible improvements and addressing the existing imperfections. However, the microwave radiometer operations to observe the cryosphere are very far from ideal. Firstly, they are limited to a few narrow frequency bands to avoid interference from active remote sensing sources such as radars and other wireless communication systems. Also, electrical properties of the firn, which, does determine the amount of electromagnetic radiation emitted, have also not been fully characterized in terms of frequency and temperature. So, this work includes modelling the electrical properties of the firn through a wide range of frequency and temperature, for which the complex permittivity of ice is measured across frequency range 0-50 GHz and temperature range 200-273K (∼ -70 °C -0 °C) for electrical characterization. However, due to sensitivity issues of the measurement setup to accurately measure the small subtle changes in the imaginary part of the complex permittivity of ice, only the real part is considered and a new model for the real part of complex permittivity of ice is proposed. This novel permittivity model for ice serves as a foundation for reevaluating the existing forward electromagnetic emission model. It allows for a comparison of enhanced simulated results with satellite measurements and reassesses the retrieval of firn parameters based on the improved emission model. The goal is to achieve more accurate results, with additional aspects to be explored in future work. Lastly, these retrieved parameters would further help in radiometer designs and deployments in terms of optimal measurement frequencies as well as calibration, accuracy, sensitivity, and sampling requirements, contributing to holistic research in future.

License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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Available for download on Sunday, July 11, 2027

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