Observing global ocean circulation with SEASAT altimeter data

Abstract

A nondynamic algorithm for correcting the geo‐centric radius of the SEASAT orbit has been developed. This scheme reduces the satellite altitude error to a few decimeters and requires only weak a priori knowledge of sea surface undulations. Application has been made to a single three‐day period during which SEASAT took global altimeter measurements of sea surface topography with geographic resolution of 900 km at the equator. The resulting corrected SEASAT ephemeris then enabled computation of a sea surface largely free of the 2 to 7 m error that would otherwise arise from error in the ephemeris distributed with the SEASAT data. Subsequent subtraction of GEM L2 geoid heights from this sea surface has yielded ocean dynamic heights in reasonable qualitative and quantitative agreement with values obtained from oceanographic data. The fact that results of this quality could be obtained from only one three‐day arc of SEASAT data demonstrates the potential of satellite altimetry for determining global ocean circulation. The results also show that the solution to the problem of ephemeris error is to be found by considering both dynamic and nondynamic orbit determination methods.