Data Assimilation in a Strongly Nonlinear Ocean Model

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Proposal Number: 0137169PI: R. Miller, OSUThe physics governing the many paths of the Kuroshio will be investigated using dynamical systems analysis of barotropic and baroclinic quasigeostrophic model solutions. The dynamical systems tools will be used to determine the qualitative nature of model simulations of the Kuroshio's path off the coast of Japan. A baroclinic quasigeostrophic regional model and its adjoint will be used comparatively with existing solutions from previous model studies. It is expected that the bifurcation diagram will be similar between the barotropic and baroclinic systems but that the solutions will exhibit significant baroclinic effects. The adjoint of the baroclinic quasigeostrophic model will be used to investigate the sensitivity of the model to different types of perturbations and to determine the influence of assimilation of observations on the model predictions in each different small and large meander case. The data assimilation study will also help determine which observations predict the transition from one state to another. In addition, this portion of the study will help discriminate between the adequacies of different physics in different models for representing the natural variability of the system. This study will lead to a better understanding of the Kuroshio system off Japan, the different physical mechanisms that generate bimodality of the Kuroshio, and it has the potential to yield guidance towards the critical set of observations that capture the behavior of the system.