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Improved estimation of ocean wave fields from marine radars using data assimilation techniques

Real-time sea state measurements could be used to greatly enhance the safety and efficiency of offshore operations. In this paper, a variational data assimilation scheme is developed to improve ocean wave field estimates from marine navigation radars. The assimilation scheme minimizes a cost function which is defined as the difference between radar observations and predictions from a nonlinear wave evolution model over a time interval which is referred to as assimilation interval. An adjoint method is used to calculate the gradient of the cost function with respect to control variables, and the descent direction for minimization is obtained from tangent linear model. The proposed assimilation scheme is validated using synthetic and field data.