| In this thesis, studies were carried out on the theoretical schemes of data assimilation and their applications on sea fluid field, the three-dimensional baroclinic primitive equation model-Hamburg Shelf Ocean Model (HAMSOM)-being one part of the three ones that constitute the data assimilation (DA) system. Effective modification on schemes of DA were obtained and applications on TOPEX/POSEIDON (T/P) data results that covering the area of Yellow Sea and East Sea were done. The final results became closer to the objective nature.Studies on DA schemes and their applications were detailed on the basis of existed literatures, the studies of applications on China Sea being rather poor at the moment. The final results obtained in this paper contained that the optimal interpolation scheme highlighted by the covariance that the correlation between different time and the correlation between different place being considered; that the simplification of Kalman Filter with the singular-value decomposition (SVD) and the direct construction of state transition matrix pfeceded with "inverse vector expression"; and that the analysis of T/P data and its blending with theoretical model. They are detailed as follows:1. To construct covariance matrix with time correlation and distance correlation.Both observational data and theoretical model results has its respective errors, upon which both covariance matrix being produced. The matrices are the bridge that linkedd the observational data with the theoretical model results together. When made covariance matrix, the observational data were always treated as one group without considering the time misfit, which did not match the true situation. In this thesis not only the distance, but also the time correlation was taken into account when constructed the covariance matrix, the observational data being treated differently according to its obtaining time and the weight, big or small, being assigned to differently according to its time correlation, strong or weak. All that done mentioned above made the application of data be closer to practical situation.2. Applied the dynamic optimal interpolation to Bohai SST.There is no consideration of time misfit in traditional optimal interpolation. In this thesis, some researches were done on the methodology of optimal interpolation, in which a new form of the formulae was developed that named dynamic optimal interpolation, the time correlation being introduced. With the applications of the new method, the weight matrix of observations can be dealt with dynamically while without losing the merits of the traditional ones, and the time correlation can be taken into account in real time when computing the weight matrix, which overcome the problem of time misfit between observations and forecasts. A test arranged to check lately and the result indicates that thenew method can work efficiently, that the results were closer to the objective nature.3. To produce a new reduced KF scheme with SVD, and construct the state transition matrix directly.Many researchers have employed Kalman Filter (KF) scheme to data assimilation, which manifests its validity in blending the model results and data. However, the major difficulty in applying the KF scheme to data assimilation is its enormous size of the system, which leads to the suboptimum in practical applications. Nowadays, many extended KF schemes have been proposed to solve the manipulation of large size of matrix. All the simplifications of KF scheme followed the same rule, that is, kept the major information most possibly and simplified the calculation possibly. In our study, we adopt another new method to reduce the dimensions of state space variables and then obtain a new way to simplify the calculation of KF gain. With the new method, we not only obtain the results that have the same expression forms as those of literatures existed, but also deduce the new equations that can be used to evaluate the abandoned parts quantitatively, which expanded the application of KF and mad...
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