The analysis of Geos 3 altimeter data in the Tasman and Coral seas

A technique has been developed for preprocessing Geos 3 altimetry data to establish a model of the regional sea surface. The algorithms as presently used develop models for 4×10 7 km 2 areas with an internal precision of ± 1 m. This figure is substantially influenced by the data acquisition period and the sea state. There are discrepancies between the sea surface model so obtained and GEM 6‐based geoid profiles with wavelengths of approximately 2500 km and amplitudes of up to 5 m in this region. The amplitudes are smaller when compared with GEM 10‐based geoid determinations. However, the comparison of 14 pairs of overlapping passes in the region indicates altimeter resolution at the ±25‐cm level if the wavelength corresponding to the Nyquist frequency was 30 km. In most cases the spectral analysis of such comparisons shows significant signal strength in the discrepancies after least squares fitting, with wavelengths in excess of 200 km. Regional studies of time‐varying features of the sea surface in the data analysis area are not currently possible owing to inadequate tracking support and the limited time span over which a dense data coverage was available.