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Proceedings Paper

Wind measurement accuracy for the NASA scatterometer
Author(s): David G. Long; Travis Oliphant
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Paper Abstract

The NASA Scatterometer (NSCAT) is designed to make measurements of the normalized radar backscatter coefficient ((sigma) o) of the ocean's surface. The measured (sigma) o is a function of the viewing geometry and the surface roughness due to wind-generated waves. By making multiple measurements of the same location from different azimuth angles it is possible to retrieve the near-surface wind speed and direction with the aid of a Geophysical Model Function (GMF) which relates wind and (sigma) o. The wind is estimated from the noisy (sigma) o measurements using maximum likelihood techniques. The probability density of the measured (sigma) o is assumed to be Gaussian with a variance that depends on the true (sigma) o and therefore the wind through the GMF and the measurements from different azimuth angles are assumed independent in estimating the wind. In order to estimate the accuracy of the retrieved wind, we derive the Cramer-Reo (CR) bound for wind estimation from scatterometer measurements. We show that the CR bound can be used as an error bar on the estimated wind. The role of geophysical modeling error in the GMF is considered and shown to play a significant role in the wind accuracy. Estimates of the accuracy of NSCAT measurements are given along with other scatterometer geometries and types.

Paper Details

Date Published: 18 September 1997
PDF: 9 pages
Proc. SPIE 3117, Earth Observing Systems II, (18 September 1997); doi: 10.1117/12.278915
Show Author Affiliations
David G. Long, Brigham Young Univ. (United States)
Travis Oliphant, Brigham Young Univ. (United States)

Published in SPIE Proceedings Vol. 3117:
Earth Observing Systems II
William L. Barnes, Editor(s)

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