Validation of Sea Level Data in the East Asian Marginal Seas:Comparison between TOPEX/POSEIDON Altimeter and In-Situ Tide Gauges

In an effort to assess the reliability of satellite altimeter systems, the authors conduct a comparativeanalysis of sea level data that were collected from the TOPEX/POSEIDON (T/P) altimeter and 10 tidegauges (TG) near the satellite passing ground tracks. The analysis is made using datasets collected frommarginal sea regions surrounding the Korean Peninsula at T/P cycles of 2 to 230, which correspond toOctober 1992 to December 1998. Proper treatment of tidal errors is a very critical step in data processingbecause the study area has very strong tide. When the T/P data are processed, the procedures of Parkand Gamberoni (1995) are adapted to reduce errors associated with the tide. When the T/P data areprocessed in this way, the alias periods of M2, S2, and K1 constituents are found to be 62.1, 58.7, and 173days repectively. The compatibility of the T/P and TG datasets are examined at various filtering periods.The results indicate that the low-frequency signals of the T/P data can be interpreted more safely withlonger filtering periods (such as up to the maximum selected value of 200 days). When RMS errors forthe 200-day low-pass filter period are compared with all 10 tidal stations, the values span the range of2.8 to 6.7 cm. The results of a correlation analysis for this filtering period also show a strong agreementbetween the T/P and TG datasets across all stations investigated (e.g., p-values consistently less than0.001 ). Hence according to the analysis, the conclusion is made that the analysis of surface sea level usingsatellite altimeter data can be made safely with reasonably extended filtering periods such as 200 days.