Study On The Development Of Ocean Current Forecasting System For Olympic Sailing In Qingdao

The research purpose of this thesis is to develop an ocean current forecasting system,which can be used to forecast the hydrodynamic condition in the sea marked out for the Olympic Sailing.There are two aims for the developing system.First,it is able to offer high precision forecasting of ocean current.Second,it can be taken as important framework for an operating forecasting system.Therefore,this paper is focused on the following two efforts:ocean current modeling with high resolution and assimilation research in forecasting system with spot survey data.The application of grid nesting technology is essential to the forecasting system. Reasons are illustrated here.It is well known that,large space and long time dimensions are needed for circulation current modeling needs.However,smaller and shorter dimensions are expected in tidal current modeling.In addition,the current forecasting for the Olympic Sailing requires quality of high resolution.It means that many more grids are needed to depict the same sea area.Finally,the model is required to give forecasting results in time.So nested-grid method is a good idea to make the model run faster.Firstly,POM is used to set up a model with the ability of nested-grid modeling. According to forecasting scheme,two independent nested-grid models are needed. One works on the large and middle modeling domain.The other works on the middle and small modeling domain.The difference between the two models above is only with different methods of input data and open boundary control.Then a three dimensional baroclinic forcasting model is completed through united running of the two independent models.Thus,the united model is able to model the circunlation over the concerned sea with high resolution.Further,tidal current should be considered in the forcasting system too.Secondly,in order to improve the forecasting results,assimilation method of Newtonian nudging is considered in the forecasting system.Newtonian nudging is very flexible to make use of many kinds of survey data.In Newtonian nudging, relaxation coefficient is very important.But it is often fixed with much subjectivity.It is difficult to find out the accurate value.In this paper,different relaxation coefficients are given in different modeling cases.Then their modeling results are compared with the survey data.So it is easy to find out which best one to improve the forecasting results.In the end,it has been finished to set up the high resolution ocean current forcasting system now.On the basis of that,assimilation module is completed too. Some modeling results are compared with survey data,such as current velocities from buoys.It indicates that the forecasting results are closed to the real situation.So the output of the forcasting system is believable.However,it seems that assimilation module does not work well.Many reasons should be considered.For instance,maybe it is better to control the survey data quality.Maybe much more time and research work are needed for the forcasting system.