A geosat altimeter wind speed algorithm and a method for altimeter wind speed algorithm development

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  • A Geosat altimeter wind speed algorithm is derived by cross-calibrating Geosat and Seasat altimeter estimates of the normalized radar cross section σ₀ and modifying an existing Seasat altimeter wind speed model function to obtain a model function appropriate for Geosat observations. It is argued that the σ₀ distribution measured by an altimeter is relatively stable over a sufficiently large geographical region and a long enough time period. Systematic differences between σ₀ estimates from two altimeters can therefore be identified based on comparisons of their σ₀ histograms. Any such systematic differences can then be corrected using independent σ₀ estimates. When this method is applied to the Geosat and Seasat altimeters, a systematic difference between the two σ₀ histograms is shown to be consistent with differences between Seasat altimeter and nadir Seasat scatterometer estimates of σ₀ deduced independently by a previous study. This supports the conclusions that (1) the σ₀ distribution is stable, and (2) the Seasat altimeter estimates of σ₀ were miscalibrated. After modifying the existing Seasat altimeter wind speed algorithm to account for this apparent σ₀ error, the resulting Geosat estimates of wind speed agree with high-quality buoy observations to within an rms difference of less than 2 m/s.
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  • Witter, D., and D. Chelton (1991), A Geosat Altimeter Wind Speed Algorithm and a Method for Altimeter Wind Speed Algorithm Development, J. Geophys. Res., 96(C5), 8853-8860.
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  • 96
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  • C5
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