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Multi-frequency Atmospheric Refractivity Inversion Dissertation

Xu, Luyao
http://orcid.org/0000-0001-6651-1477
http://rave.ohiolink.edu/etdc/view?acc_num=osu1574550558934232

Abstract Details

2019, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
The interaction between the ocean and lower troposphere in the marine atmospheric boundary layer produces rapid moisture and temperature inversions, which creates atmospheric ducts. Electromagnetic (EM) waves can be entrapped within the duct layers and propagate more efficiently than in normal conditions. The effects of the duct on EM wave propagation result in longer propagation range, signal fades at specific locations, and increased radar clutter. Also, the propagation effects strongly vary with frequency in the nonstandard atmosphere. Hence, good characterizing of the localized refractivity structure is essential to understand the propagation abilities of radio wave communications and radar systems. This dissertation addresses lower atmospheric refractivity inversions from multi-frequency EM measurements, analyzes the accuracy of a numerical weather prediction model over a wide frequency range. The Lower Atmospheric Propagation Ultra-Wide Band (LATPROP-UWB) system is designed and built to measure EM propagation over a long distance for 2 to 40 GHz. The system was deployed during the Coupled Air-Sea Processes and EM Ducting Research (CASPER) East and West Campaigns. In CASPER East, range-dependent propagation loss (PL) up to 55 km was collected. With the upgraded system, fixed link PL was recorded during Casper West. Multi-frequency inversion algorithms are developed to estimate the refractivity profiles. The parabolic wave equation method is used to model EM wave propagation along long-range in low grazing angle. Extensive and concurrent meteorological measurements collected during both CASPER Campaigns are used to evaluate the inversion results. The estimation accuracy improves with a larger number of frequencies in both simulation and measured results. The multi-frequency system also makes the retrieval less dependent on varying environmental conditions when some frequencies are not sensitive to atmospheric conditions. The inversion results show that optimal refractivity retrieval can be achieved with ten frequencies. This also results in a fourfold reduction in the estimation RMS error compared to a single-frequency inversion. Large scale environment modeling for the CASPER Campaigns was made by Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS). The forecast accuracy of COAMPS in EM propagation is assessed, and it is concluded that the accuracy degrades with longer forecast length and higher frequency. Also, higher horizontal resolution does not result in significant improvement, and higher time resolution smooths the PL pattern with range but only slightly reduces the PL error. The parabolic wave equation is also linearized to formulate refractivity estimation in a compressed sensing framework. A simulation example demonstrates that this estimation method works for surface based duct conditions with a close prior. The work has been done in this dissertation studied the effects of ducting on broad frequency bands and used multi-frequency to retrieve refractivity profiles. This study will benefit the communication system design in non-standard atmospheric conditions.
Caglar Yardim (Advisor)
Robert Burkholder (Committee Member)
Joel Johnson (Committee Member)
Fernando Teixeira (Committee Member)
Jennifer Leight (Committee Member)
177 p.
Atmosphere; Electromagnetics; Remote Sensing

Recommended Citations

Citations

  • Xu, L. (2019). Multi-frequency Atmospheric Refractivity Inversion Dissertation [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574550558934232

    APA Style (7th edition)

  • Xu, Luyao. Multi-frequency Atmospheric Refractivity Inversion Dissertation. 2019. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1574550558934232.

    MLA Style (8th edition)

  • Xu, Luyao. "Multi-frequency Atmospheric Refractivity Inversion Dissertation." Doctoral dissertation, Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574550558934232

    Chicago Manual of Style (17th edition)

osu1574550558934232
94
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This open access ETD is published by The Ohio State University and OhioLINK.