Visual demonstration of three-scale sea-surface roughness under light wind conditions

During the Southern Ocean Waves Experiment (SOWEX) an aircraft carried a down-looking video camera to help document the sea surface. Reflected images of the aircraft were intermittently observed in the video recorded at 15-30-m height under light and variable wind conditions. A numerical simulation...

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Bibliographic Details
Published in:IEEE transactions on geoscience and remote sensing 2005-08, Vol.43 (8), p.1751-1762
Main Authors: Walsh, E.J., Banner, M.L., Churnside, J.H., Shaw, J.A., Vandemark, D.C., Wright, C.W., Jensen, J.B., Sunhee Lee
Format: Article
Language:English
Subjects:
Aircraft
Altimeters
Applied geophysics
Cameras
Computer simulation
Earth sciences
Earth, ocean, space
Estimates
Exact sciences and technology
Internal geophysics
Light wind
Marine geology
mean square slope (MSS)
microwave
Numerical simulation
Ocean waves
optical
Radar imaging
Rough surfaces
Roughness
Sea surface
Southern Ocean
Surface roughness
Surface waves
Wind speed
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Summary:During the Southern Ocean Waves Experiment (SOWEX) an aircraft carried a down-looking video camera to help document the sea surface. Reflected images of the aircraft were intermittently observed in the video recorded at 15-30-m height under light and variable wind conditions. A numerical simulation was developed to relate image contrast to the gravity-capillary wave contribution to sea-surface mean square slope (mss). "Carnival fun-house" mirror-type distortions of the image in the absence of the gravity-capillary waves relate to intermediate-scale wave persistence when wind forcing stops. Video image estimates of mss correlated better with 36-GHz scanning radar altimeter estimates than with the wind speed measured at 30-m height. When the gravity-capillary waves disappeared in the absence of wind forcing, about one-third of the 0.0015 residual mss was contributed by the dominant waves, and about two-thirds was contributed by the 1-10-m wavelength region. Near the shores of a lake in Alaska, reflected aircraft images were also observed, indicating that the gravity-capillary wave contribution to mss was only about 0.000 001, even though the wind speed at the 160-m aircraft height was 10 m/s.
ISSN:0196-2892
1558-0644
DOI:10.1109/TGRS.2005.851633