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Measurements of electromagnetic bias at Ku and C bandsThe electromagnetic (EM) bias epsilon is an error present in radar altimetry of the ocean surface due to nonuniform reflection with surface displacement. The electromagnetic bias is defined as the difference in height between the mean reflecting surface and the mean sea surface. A knowledge of the electromagnetic bias is required for reducing errors in mean sea level measurements by satellite radar altimeters. Direct measurements of the EM bias at 14 GHz (Ku band) and 5 GHz (C band) were made from an oil production platform in the Gulf of Mexico over a 6-month period during 1989 and 1990. A total of 1280 hours of usable data was collected. During the experiment the significant wave height (SWH) varied from 0.6 to 3.2 m; the wind speed at 25 m above the surface varied from 0.1 to 14.3 m/s; the Ku band bias varied from -1.0 to -13.8 cm, or from -1.6% to -5.3% of the SWH; and the C band bias varied from -0.4 to -19.9 cm, or from -0.6% to -6.3% of the SWH. The biases has mean values of -3.7% and -3.6% of SWH with standard deviations of the variability about the mean of 0.7% and 1.0% of the SWH for Ku and C bands, respectively. We found a nonlinear relationship between dimensionless bias (bias/SWH) and wind speed at both low and high wind speeds. For wind speeds less than 3-4 m/s but less than 10 m/s, both biases were found to increase linearly with wind speed. For wind speeds greater than 11-12 m/s, the C band bias reaches a maximum. The Ku band bias reaches a maximum and then begins to decrease for wind speeds greater than 9-10 m/s.
Document ID
19950040937
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Arnold, D. V.
(Brigham Young Univ. Provo, UT, United States)
Melville, W. K.
(Scripps Institution of Oceanography, La Jolla, CA United States)
Stewart, R. H.
(Texas A&M Univ. College Station, TX, United States)
Kong, J. A.
(MIT, Cambridge, MA United States)
Keller, W. C.
(Univ. of Washington, Seattle, WA United States)
Lamarre, E.
(MIT, Cambridge, MA United States)
Date Acquired
August 16, 2013
Publication Date
January 15, 1995
Publication Information
Publication: Journal of Geophysical Research
Volume: 100
Issue: C1
ISSN: 0148-0227
Subject Category
Oceanography
Accession Number
95A72536
Distribution Limits
Public
Copyright
Other

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