A theory of the Kaband radar imaging mechanism of a submerged wreck and associated bed forms in the southern North Sea

Hennings, Ingo and Herbers, Dagmar (2010) A theory of the Kaband radar imaging mechanism of a submerged wreck and associated bed forms in the southern North Sea Journal of Geophysical Research: Oceans, 115 (C10). C10047. DOI 10.1029/2010JC006360.

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Abstract

The Ka band radar imaging mechanism of the submerged wreck/sand ribbon of the
motor vessel (M/V) Birkenfels in the southern North Sea is investigated by applying
the quasi‐specular scattering theory and considering the capillary as well as the gravity
wave ranges of the wave energy density spectrum. For the imaging of wrecks and
other oceanographic and meteorological phenomena at the sea surface it is assumed that
quasi‐specular scattering becomes dominant at higher radar frequencies like Ka and X
band and wind speeds ≥ 7–8 m s−1. Multibeam echo sounder images of the Birkenfels
wreck and associated sand ribbons as well as other available environmental in situ data
have been analyzed. The formation of sand ribbons at the sea bed and the manifestation
of its radar signatures at the water surface are caused by an elliptical vortex or helical
flow cell triggered by unidirectional tidal current flow interacting with the wreck. The
difference between simulated and measured normalized radar cross section (NRCS)
modulation as a function of the space variable is less than 31.6%. Results are presented
for NRCS simulations dependent on position for different effective incidence angles,
unidirectional current speeds, wind speeds, and relaxation rates. The calculated current
gradient or strain rate of the imaging theory has the same order of magnitude as those
obtained for marine sand waves. This implies that the responsible hydrodynamic
interaction mechanism is able to produce radar signatures of submerged wrecks/sand
ribbons and make them visible at the sea surface.

Document Type: Article
Keywords: Seismology; submerged wreck, residual flow circulation, real aperture radar (RAR), normalized radar cross section (NRCS) modulation, quasi-specular scattering theory
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
DOI etc.: 10.1029/2010JC006360
ISSN: 2169-9275
Date Deposited: 23 Nov 2010 11:20
Last Modified: 27 Feb 2018 09:57
URI: http://eprints.uni-kiel.de/id/eprint/10055

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