DETERMINATION OF OPEN BOUNDARY-CONDITIONS WITH AN OPTIMIZATION METHOD

The optimization method proposed in this paper is for determining open boundary conditions from interior observations. Unknown open boundary conditions are represented by an open boundary parameter vector (B), while known interior observational values are used to form an observat ion vector (O). For a hypothetical B (generally taken as the zero vec tor for the first time step and as the optimally determined B al the p revious time step afterward), the numerical ocean model is integrated to obtain solutions (S) at interior observation points. The root-mean -square difference between S and O might not be minimal. The authors change B with different increments delta B. Optimization is used to g et the best B by minimizing the error between O and S. The proposed op timization method can be easily incorporated into any ocean models, wh ether linear or nonlinear, reversible or irreversible, etc. Applying t his method to a primitive equation model with turbulent mixing process es such as the Princeton Ocean Model (POM), an important procedure is to smooth the open boundary parameter vector. If smoothing is not used , POM can only be integrated within a finite period (45 days in this c ase). If smoothing is used, the model is computationally stable. Furth ermore, this optimization method performed well when random noise was added to the ''observational'' points. This indicates that realtime da ta can be used to inverse the unknown open boundary values.