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Electromagnetic Backscattering Studies of Nonlinear Ocean Surfaces
Pan, Guangdong

2008, Doctor of Philosophy, Ohio State University, Electrical Engineering.

The spatial/time spectrum of short sea waves and radar observed signals are locally modulated by the presence of longer waves or currents. There are two
different modulations: tilt modulation and hydrodynamic modulation. Variations
in the short sea waves spectrum are described by the "hydrodynamic
modulation transfer function" (HMTF). The nonlinear interaction between short
sea waves and longer waves makes such modulation. Variations of radar
signals are described by the "radar modulation transfer function" (RMTF). In this study, new numerical methods based on numerical
nonlinear hydrodynamics and computational electromagnetics are developed
to examine modulation in sea surface scattering and to examine the accuracy
of existing analytical models.


Electromagnetic scattering from sea surface at low-grazing-angles (LGA) is
studied by comparing analytical scattering models. The two-scale model
(TSM) is found to yield the most reasonable performance among these models.
Ocean surface profile retrieval based on the TSM is also shown to have an acceptable accuracy.


Numerical methods are developed to calculate the HMTF, and RMTF by use
of the fast nonlinear hydrodynamics, and by use of the fast computational
electromagnetics techniques. These techniques allow us to study the
scattering from a stochastic "Pierson-Moskowitz" like surface with Monte-Carlo
simulation.


HMTF values obtained from the simulations are compared to those from a first
order wave action solution, and found to be in reasonable agreement, although
differences on the order of 10% are observed. A numerical evaluation of
long wave effects on the short wave dispersion relation is also provided.


The numerical method provides a quantitative way to examine the "third-
scale" effect in the two-scale model. The results demonstrate that the
intermediate waves influence the RMTF and are modulated by longer waves.
This effect explains the RHMTF polarization dependence. Numerical results of
the "third-scale" effect match well with empirical and analytical results.


A new analytical Doppler formula is derived from the nonlinear hydrodynamics.
The solution is validated by numerical solutions and supported by radar
Doppler simulation. Ocean surface profile retrieval based on Doppler
information is shown to have a very good accuracy.


Joel Johnson, Ph.D (Advisor)
185 p.

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Pan, G. (2008). Electromagnetic Backscattering Studies of Nonlinear Ocean Surfaces. (Electronic Thesis or Dissertation). Retrieved from https://etd.ohiolink.edu/

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Pan, Guangdong. "Electromagnetic Backscattering Studies of Nonlinear Ocean Surfaces." Electronic Thesis or Dissertation. Ohio State University, 2008. OhioLINK Electronic Theses and Dissertations Center. 25 Nov 2017.

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Pan, Guangdong "Electromagnetic Backscattering Studies of Nonlinear Ocean Surfaces." Electronic Thesis or Dissertation. Ohio State University, 2008. https://etd.ohiolink.edu/

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