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Airborne microwave Doppler measurements of ocean wave directional spectraA technique is presented for measuring ocean wave directional spectra from aircraft using microwave Doppler radar. The technique involves backscattering coherent microwave radiation from a patch of sea surface which is small compared to dominant ocean wavelengths in the antenna look direction, and large compared to these lengths in the perpendicular (azimuthal) direction. The mean Doppler shift of the return signal measured over short time intervals is proportional to the mean sea surface velocity of the illuminated patch. Variable sea surface velocities induced by wave motion therefore produce time-varying Doppler shifts in the received signal. The large azimuthal dimension of the patch implies that these variations must be produced by surface waves traveling near the horizontal antenna look direction thus allowing determination of the direction of wave travel. Linear wave theory is used to convert the measured velocities into ocean wave spectral densities. Spectra measured simultaneously with this technique and two laser profilometers, and nearly simultaneous with this technique and two laser profilometers, and nearly simultaneous with a surface buoy, are presented. Applications and limitations of this airborne Doppler technique are discussed.
Document ID
19870051906
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Plant, W. J.
(Naval Research Lab. Washington, DC, United States)
Keller, W. C.
(Naval Research Lab. Washington, DC, United States)
Reeves, A. B.
(Naval Research Lab. Washington, DC, United States)
Uliana, E. A.
(U.S. Navy, Naval Research Laboratory, Washington DC, United States)
Johnson, J. W.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 13, 2013
Publication Date
March 1, 1987
Publication Information
Publication: International Journal of Remote Sensing
Volume: 8
ISSN: 0143-1161
Subject Category
Oceanography
Accession Number
87A39180
Distribution Limits
Public
Copyright
Other

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