Research On A Storm Tide Prediction Model And Its Application

The change of water level is influenced not only by astronomic tide but also bymeteorological factors in the shelf zone. Typhoon, among others, often leads tosignificant setup or set-down of water level in the nearshore zone and bringsdisastrous influences on the people in coastal zone. China is one of the countries thatare seriously influenced by storm tide. Thus, development of a storm tide numericalmodel that is fit to the dynamic conditions of Chinese ocean is of great importance.In this paper, an astronomic tide prediction model is first established by using a3-D ocean hydrodynamic model—COHERENS for the Bohai Sea region. By usingthe provided harmonic analysis tool and some collected measurements of tideconstituent parameters of several tide stations, the tide parameters of the four tideconstituents are obtained through try-and-error method. The distributions ofatmospheric pressure and wind velocity field are computed by using some course dataof atmospheric pressure and wind according to a simple theoretical formula.The COHERENS model can model not only tide process in Cartesian coordinatesystem in small sea region but also tide wave by in spherical coordinate system inlarge ocean zone. Because the vertical coordinate is transformed by a σtransformation, the boundary conditions of bottom and surface are simplified. Thestress in momentum equation is handled by using Boussinesq assumption. Pressureterms are handled by using static water pressure assumption. In solving the equations,Arakawa C grid is used in horizontal direction. Gravity wave water level is computedby using barotropic mode. Baroclinic mode is used to calculated depth-resolvedphysical quantities. The barotropic mode uses shorter time step, while the baroclinicmode uses longer one. All horizontal derivatives are expressed in explicit schemewhile vertical terms are expressed in implicit scheme. The advection terms arecalculated by TVD scheme with supperbee limiting function.The established model is applied to simulate the increasing of water levelinfluenced by No. 9712 tropics storm over the Bohai Sea region. The simulated waterlevel processes are compared with the measured water level processes of Tanggu andQinhuangdao tide station. The results indicate that the trends agree and the model isthus proved to be applicable in the storm tide prediction.