Analysis of sea surface topography using SEASAT altimeter data

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1983-03

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Ohio State University. Division of Geodetic Science

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The sea surface topography (SST) is required for both oceanographic and geodetic purposes. Using geodetic techniques the SST can be determined from altimeter data and knowledge of the geoid. A set of time averaged sea surface heights at 1° intersections in the oceanic areas is used, derived from the adjusted SEASAT altimeter data. A geoid corresponding to these sea surface heights is computed up to minimum wavelengths of 2000 km, using the GEML1 gravity model. A best fit ellipsoid to the mean sea surface is determined. The differences between the sea surface heights and the geoid are computed to give raw estimates of SST. These estimates contain GEML1 errors and residual geoid information. These last quantities are filtered out by using a spherical harmonic analysis and retaining the spherical harmonics up to degree 6. The primary limitation in the determination of SST for higher harmonic degrees is due to the errors of the GEML1 gravity model. A two dimensional filter has also been implied as an alternative method. Using the spherical harmonic coefficients, estimates of SST are computed and global maps of SST and current directions are constructed. The solution is compared with oceanographic solutions as well as with other satellite derived solutions.

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Prepared for National Oceanic and Atmospheric Administration, Rockville, Maryland: Contract No. 78-4326

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