Global mean sea surface computation using GEOS 3 altimeter data

Abstract

A mean sea surface map has been determined for the global ocean areas between +62° and −62° latitude using GEOS 3 altimeter data. A grid of laser reference orbits computed using the GEM 10B gravity model has been used to orient the altimeter data in a center of mass coordinate system. The density of the altimeter tracks has enabled the computation of the sea surface heights above the reference ellipsoid on a 1°×1° grid in most of the oceanic areas. In the northwest Atlantic the dense coverage has enabled computations on a 0.25°×0.25° grid. Comparisons of the global surface with an independently computed mean sea surface based upon SEASAT altimeter data indicate an rms agreement of a little over a meter. Comparisons of the regional solution in the northwest Atlantic with SEASAT profiles indicate a precision of a few decimeters in this surface. An analysis of the global crossover differences has indicated the possibility of a timing error in the altimeter data. Timing bias values of 9.2±0.5 ms for 1975 and 18.7±0.6 ms for 1976 have been recovered from an analysis of the altimeter data.

Radial variations of a satellite orbit due to gravitational errors: Implications for satellite altimetry

“…As we saw in the last section, without substantial geopotential improvement the 100-mm capability of future altimetry cannot be fully utilized because of unresolved radial orbit errors. Since the advent of satellite altimetry a popular empirical solution to the "orbit error problem" has been to use differences of altimetric heights at track crossovers [e.g., Rapp, 1983;Marsh et al, 1982]. These differences contain no permanent sea surface information, only time-varying orbit and tidal errors and oceanic effects from eddys, meanders, rings, and atmospheric storms.…”

The SEASAT altimeter mean sea surface model

“…A contour map of the differences between the SS4 mean sea surface and the GEM 10B gravimetric geoid indicated that most of the large differences occtlr over short-wavelength features which cannot be modeled by the GEM 10B In an attempt to provide insight into the source of these differences, further comparisons have been performed with another global mean sea surface recently computed by Marsh et al [1981] based upon the 1975-1976 GEOS 3 altimeter data. The GEOS 3 reference orbits were computed using the GEM 10B [Lerch et al, 1981] gravity model.…”

Circulation in the Gulf of Mexico from Geosat altimetry during 1985–1986

“…After initial examination of the data, we concluded that some residual radial orbit error remained, i.e., several tracks contained excessively large biases. Radial orbit error is predominantly long wavelength, comparable to the Earth's circumference (one unresolved "bounce" per revolution), and is commonly removed with a tilt and bias correction [e.g., Marsh et al, 1982]. Tai [1989] has examined the consequences of removing (1) bias only, (2) bias and tilt, and (3) bias, tilt, and curvature from different arc lengths.…”