Journal of Oceanography, Vol. 53, pp. 303 to 309. 1997 303 Copyright  The Oceanographic Society of Japan. Short Contribution Keywords: ⋅ Tidal chart, ⋅ altimetry, ⋅ East China Sea, ⋅ Yellow Sea, ⋅ TOPEX. Co-tidal and Co-range Charts for the East China Sea and the Yellow Sea Derived from Satellite Altimetric Data TETSUO YANAGI, AKIHIKO MORIMOTO and KAORU ICHIKAWA Department of Civil and Ocean Engineering, Ehime University, Matsuyama 790, Japan (Received 30 November 1995; in revised form 9 December 1996; accepted 10 December 1996) Co-tidal and co-range charts of eight major constituent tides in the East China Sea and the Yellow Sea are drawn from the results of the harmonic analysis of TOPEX/POSEIDON altimetric data. Those of M 2 , S 2 , K 1 and O 1 constituents agree well with the traditional ones estimated from tide gauge data at coastal stations. Those of N 2 and K 2 are similar to those of M 2 constituent and those of P 1 are similar to K 1 constituent, respectively. The amplitude of S a constituent is large and its phase leads in the shallow part of the East China Sea and the Yellow Sea. The altimetric data from TOPEX/POSEIDON manifest very useful not only in the open ocean dynamics study but also in the coastal ocean dynamics study including tidal phenomena. 1. Introduction Satellite altimetric data have been very useful for the study of open ocean dynamics (e.g. Ichikawa and Imawaki, 1994). For the analysis of long-term variability in the ocean, the tidal models devised by Schwiderski (1980), based on numerical calculation, or by Cartwright and Ray (1990), on the basis of Geosat altimetric data, have been used in order to eliminate the tidal signal from the altimetric data. Re- cently, Ma et al. (1994) developed the method by Cartwright and Ray (1990) and obtained the tidal harmonic constants at 3° × 3° over the world on the basis of TOPEX/POSEIDON altimetric data. Ma et al. (1994) assumed the same ampli- tude and phase in the horizontal scale of 3° × 3° because they wanted to increase the temporal resolution by including several satellite tracks in one mesh of 3° × 3°. Their model is called the CSR model, and is now usually used to elimi- nate the tidal signal from the altimetric data in the open ocean dynamics study. However, we cannot use their results directly in coastal seas, such as the East China Sea and the Yellow Sea (Fig. 1(a)), where the tidal waves show very complicated small scale features such as some amphidromic points and a very large horizontal gradient of tidal amplitude within the scale 3° × 3° (Nishida, 1980). In this paper, we propose a procedure by which we can estimate the tidal signal correctly from the altimetric data in the coastal sea; i.e. we carry out the tidal harmonic analysis using the altimetric data. As an example, we will take the East China Sea and the Yellow Sea where the tidal signal reaches several meters, and will estimate the tidal harmonic constants of eight major constituents there; M 2 , S 2 , N 2 , K 2 , K 1 , O 1 , P 1 and S a . 2. Altimetric Data The satellite TOPEX/POSEIDON was launched in August 1992. It has continued to acquire the altimetric data approximately every 10 days along 7 observation lines in the East China Sea and the Yellow Sea, as shown in Fig. 1(b). The data are provided as the Merged Geophysical Data Record (MGDR) by the Physical Oceanography Distributed Active Archive Center at Jet Propulsion Laboratory, U.S.A. In the present analysis, we only used the data obtained TOPEX altimeter from Cycle 1 (September 1992) to Cycle 108 (August 1995) because there was an unknown bias in the order of 20 cm between the TOPEX and POSEIDON al- timeters. (This problem was solved by NASA in July 1996, and so we can now also use POSEIDON data.) Standard data corrections including electromagnetic bias correction, ionospheric correction, dry and wet trospheric correction and solid earth tide correction were made using the values provided in the MGDR. We did not, however, carry out any procedure to remove the radial orbit error, because such correction may cause omission of the tidal component. The radial orbit error has a wave length of the circumference of the earth. Its value is about 3 cm (Fu et al., 1994), which is very small compared to the tidal signal in the East China Sea and the Yellow Sea. Another important signal related to the sea surface dynamic topography may also be missed by this correction. The data of both ascending and descending tracks are