Tide Prediction And Numerical Simulations Of Tsunami And Cold Waves On Bohai Sea

Cold wave and tsunami can cause significant water lever setup in the nearshore region and hence bring serious disastrous influence to this area. Thus it is of great significance to setup a simulation and forecasting system of water level.COHERENS model is a 3-D hydrodynamic model, which can simulate not only long period gravity wave, but also transport of physical quantity, such as sediment, contaminant, salinity and heat. The model can involve many factors, such as wind, surface wave. The model is not only applicable to Cartesian coordinate system for small computational domain, but also to spherical coordinate system for a large ocean area. Transformation of the vertical coordinate by aσcoordinate system makes the boundary conditions of bottom and surface simplified. The turbulence stresses in momentum equation are handled by using Boussinesq assumption. Pressure terms are handled by using static water pressure assumption. In solving the equation, arakawa C grid is used in horizontal direction. Momentum equation is solved by using mode split technique. All horizontal derivatives are expressed in explicit scheme while vertical terms are expressed in implicit scheme. The advection terms are calculated by TVD scheme in order to obtain high resolution of solution in large gradient situation.Harmonic analysis is performed for one year's tide level in the tide table of Dalian and Yantai to obtain tidal harmonic constants of the 170 tidal constituents by using the harmonic analysis tool in the COHERENS model. And hence the astronomic tide prediction system of Huanghai and Bohai Sea is established based on the 170 tidal constituents. By using this model, an assumed earthquake tsunami happened at the center part of Bohai Sea is simulated and the influence to the water level process at the coastal area around Bohai Sea is discussed. The characteristics of the propagation of the tsunami wave are analyzed. Then tidal level changes in Bohai Sea affected by a real processes of cold wave happened in January, 2005 are simulated and the predicted results of water level are compared with the measured results of Tanggu Hydrology Station.