Harmonic Tidal Analysis along T/P Tracks in China Seas and Vicinity

Abstract

More than 300 cycles of TOPEX/POSEIDON altimeter data covering China Seas and the West Pacific Ocean are adopted to along track harmonic tidal analyses. Special concerns are placed on the tidal aliasing problem caused by the T/P sampling rate, and a criterion for separation of constituents expressed in terms of the condition number of the normal matrix of the least squares estimator is presented. The accuracy and reliability of the results are assessed by intercomparison between the results of both ascending and descending ground tracks at crossovers, and by the comparison with in situ data of tide gauges. The comparisons indicate that the harmonic constants derived from T/P track observations are more accurate than the corresponding ones of existing global ocean models, especially, over the Yellow Sea, the East China Sea and the South China Sea, characterized as continental shelves seas and semienclosed sea, where the quality of tide information is evidently improved. The root sum squares (RSS) of differences between the parameters of 4 principal tides resulted from harmonic analyses along T/P tracks and the corresponding ones from the tidal tables of hydrography of the navy in the study area is of 7 cm in magnitude. Considering the fact that the qualities of the tidal tables are not precise enough, the precision indicated by the RSS mentioned above shows an improvemen on the tide recovery over coastal waters by the thethod used in this paper. However the along track solutions can satisfy the need for providing open boundary values to develop regional ocean tide models with assimilation techniques.