| According to the stochastic dynamic analysis results of 285 tide gauge data, long term sea level trend has a substantial spatial range, generally sea level rise has the order of ± 2mm/a, but it is changing strongly from station to station, with the 16.34mm/a maximum in Manila, whose irregular distribution is probably mainly caused by crust vertical movement. The average rising rate of the total 285 tide gauge station is 1.69mm/a.The spatial distribution of sea level variation trend resulted from T/P altimetry data shows substantial inhomogeneity, with strong regional characteristics, but there is not so strong jump in space as the result from tide gauge data. The maximum region of sea level trend appears in the west tropical Pacific, with the maximal value of about 30mm/a in the core. East Pacific is in the region of decreasing substantially, with the miminum of -20mm/a in the core. It is falling in the northwest Indian Ocean with the core value of -10mm/a. Compared with other regions it is very smooth in the Atlantic Ocean with the value of -2mm/a~5mm/a. The sea level is rising at the rate of about 2.2mm/a in global mean.Thermal expansion is responsible for much of the large-scale seasonal variations observed by TOPEX/Poseidon altimeter, especially in averaging over zonal regions and basin scales, it can count for about 80~90% of the seasonal variability in the northern hemisphere.Large discrepancies, especially in the southern hemisphere, are mainly due to the sparse temperature measurement. Another possible reason is that the TOPEX/Poseidon results are averaged over a short period, for example 10 years only, and the steric estimates are primarily based on climatological data averaged over a much longer period. The sea level height changes obtained from TOPEX/Poseidon measurement and steric estimate indicate considerably stronger seasonal signals in the northern hemisphere than in the southern hemisphere.The phase difference in global MSL variations between TOPEX/Poseidon observation and steric model prediction implies a systematic difference between them. Besides the error sources mentioned above, it may come from a variety of others, for example, the water massredistribution between the oceans, atmosphere, and continental water cycle may play significant roles on TOPEX/Poseidon observed global MSL change, which are not included in the steric estimate.The three-dimensional baroclinic model POM is used to simulate the characteristics of tide and tidal waves of Bohai Sea, Yellow Sea and East China Sea.. The horizontal grade of this model is 5'X5'. Compared with the tide gauge data of 159 stations in this region, the mean absolute deviations of amplitude and phrase of M2, S2, K|, Oj are (1.69cm, 5.03°), (3.52cm, 13.78°), (1.95cm, 4.69°) and (8.18cm, 8.34°) respectively, and with the observation of tidal current in 15 stations in this region, the mean absolute deviations of the harmonic constants of the eastward and northward components of M2 are (7.4cm/s, 12.8°)and(7.7cm/s, 11.3°); those of Ki are (3.3cm/s, 26.0°) and (3.7cm/s, 31.3°).To improve the simulation of tidal wave in Taiwan Strait, the Finite Element Model (FEM) of QUODDY is appliedwith a more realistic boundary, which the north open boundary condition is provided with the results of POM in the East China Sea. Based on the numerical simulation results, the characteristics of tide and tidal currents in Taiwan Strait are analysed. Compared with the tide gauge data of 37 stations in the area, the mean absolute deviations of amplitude and phrase of M2, S2, K,, Oi are(7.35cm, 9.01°), (5.77cm, 21.52°), (3.69cm, 8.28°) and (3.58cm, 5.33°) respectively, and with the analysis result of tidal current in 5 current observation stations in the study region, the mean absolute deviations of the harmonic constants of the eastern and northern components of M2 are (lO.lcm/s, 29.8° )and(12.2cm/s, 30.2° ),and those of Ki are(5.3cm/s, 47.7° ) and (5.7cm/s, 49.8° ).Great controversy remained in the previous numerical modeling about the cotidal distribution of the maximum tidal current of M2 constituent. This paper confirms that there is an area with dense cotidal lines of M2 constituent and the northward wave of M2 constituent is more important than the southward one.For the study of the effect of the long term sea level variation on the tidal wave within East China Sea, numerical simulation experiment is made on the tidal wave in the studying area, provided a sea level rise of 60cm. It is concluded that mean sea level variation affects tidal waves markedly in the East China Sea, such effect includes the variations of both the amplitude and the tidal wave propagation. The Numerical simulation result and the harmonicanalysis result of tide gauge data agree very well and validate the above conclusion. Generally speaking, the tidal amplitude varies in the same phase with mean sea level variation, but it decreases with rising mean sea level in some regions. For example the area north of Yangtze River estuary is a typical region where tidal amplitude decreases as mean sea level rises. The maximal variation area is along Fujian and Zhejiang coast, the amplitude of M2 increases by about 12cm with a sea level rise of 60cm. The north coast of Jiangsu, the south east coast of Shandong, and the south east coast of Liaoning are the other areas influenced dramatically.Generally, the phase-lag decreases as mean sea level rises, but the variation range is small. The areas where the tidal phase-lag increases with rising mean sea level are all very limited and near corresponding amphidromic points. The spatial distribution of such variation is slightly different between diurnal tides and semi-diurnal tides.
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