A Study On Numerical Simulation And Forecast Of Tides And Tidal Currents In Xiamen Bay And Its Adjacent Waters

A three-level nested, three-dimensional numerical model of Regional OceanModeling System (ROMS) is used to investigate the tides and tidal currents aroundTaiwan Strait, southern waters of Fujian Province, and Xiamen Bay, especially for theTaiwan Strait and Xiamen Bay. The model results of large area are in good agreementwith the tidal harmonic constants of27gauge stations and harmonic forecast resultsof2tidal current observations around Taiwan Strait. At the same time, the small arearesults are consistent with the harmonic constants of5tidal stations and1successivetidal current site.Based on the computed results in the Taiwan Strait, the cotidal charts, tidalellipses, and tidal energy fluxes of four principle constituents (M2, S2, K1and O1) aredrawn to make some analysis. A semi-diurnal tide is remarkable in most areas of theTaiwan Strait, and the semi-diurnal tidal waves enters into the Taiwan Strait from thenorthern and southern parts respectively and collide in the western part of centralTaiwan Strait. The diurnal tide is less important than the semi-diurnal tide in mostcases, except in the southern part of Taiwan Strait, and the diurnal tidal wavespropagate throughout the Taiwan Strait from north to south. What’s more, Theamplitude of M2constituent is larger from north and south to the central section, withthe maximum amplitude in the Xinghua Bay west of the Taiwan Strait. Twoamphidromic points are shown around the Taiwan Shallow in the S2cotidal chart.Amplitudes of K1and O1are more obvious in the western part than in the eastern partof the strait. The surface tidal currents rotate counterclockwise in the northern andcentral part of Taiwan Strait, while clockwise in the southern part. The rotating tidalcurrents are superior to the rectilinear ones. Besides, the northern part of semi-diurnalwaves can reach the Taiwan Shallow, while the southern one influences the areasaround Penghu Islands. The northern part of diurnal waves impacts all over theTaiwan Strait. According to the nested model results around Xiamen Bay, some conclusions aremade as follows through detailed analyzing the characteristics of tides, tidal currents,tide-induced residual currents, tidal energy fluxes and tidal range. A regularsemi-diurnal tide is exhibited around Xiamen Bay. Degenerate rotating tidal currentsare found off Xiamen Bay and progressive tidal currents are found in Xiamen Bay.The surface tidal currents of four main constituents (M2, S2, K1and O1) rotatecounterclockwise off Xiamen Bay, while flow rectilinearly along the channel ofXiamen Bay. During the flood tide the tidal currents flow through East Channel offNorth Jinmen Island, Jinmen Channel, East Channel off Xiamen Island, QingyuChannel and other channels into Tongan Bay and Jiulongjiang Estuary northwardlyand northwestwardly. During the ebb tide, the tidal currents flow out through theabove-mentioned channels into the Taiwan Strait southwardly and southeastwardly.The pattern of the surface residual currents is consistent with the pattern of the bottomresidual currents, while the former velocity is larger than the latter. The tidal energyfluxes of M2, S2, K1and O1transported from the Taiwan Strait to the channels, innerbays and estuarine area in Xiamen waters are114.0MW,13.5MW,3.5MW and1.1MW, respectively. Besides, the tidal prism of the channels, inner bays andestuarine area in Xiamen waters is estimated to be2.41×109m3during moderate tideand4.72×109m3during spring tide.Comparison validation and feature analysis indicate that the nested model resultsare believable, reliable, practical, and of high precision, especially for the watersaround the Xiamen Bay. Accurate and real-time numerical forecast of tides and tidalcurrents is made by running the nested model, which is provided as standard databasefor emergency forecast system like oil spilling and saving.