A COMPARISON OF MONTHLY MEAN SEA-LEVEL VARIABILITY DETERMINED FROM GEOSAT ALTIMETRY AND A GLOBAL TIDE-GAUGE DATASET

Monthly mean sea surface heights derived from precise global orbit recomputations for the first year of the Geosat Exact Repeat Mission have been compared to tide gauge data from 57 island and 71 coastal sites. In general, the monthly means from the different techniques are correlated significantly at island stations, especially in the Tropical Pacific, and the average standard deviation of the monthly mean differences between techniques is 5cm. This provides a conservative estimate of the current accuracy of deriving monthly mean sea surface topography time series from altimetry. Coastal gauge data in general have a weaker correlation with the nearby deep ocean altimeter data, although groups of stations in the western Pacific do exhibit significiant correlation.