A 4DVAR System for the Navy Coastal Ocean Model. Part 1: System Description and Assimilation of Synthetic Observations in Monterey Bay
NAVAL RESEARCH LAB CHESAPEAKE BEACH MD CHESAPEAKE BAY DIV
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A 4D variational data assimilation system was developed for assimilating ocean observations with the Navy Coastal Ocean Model. It is described in this paper, along with initial assimilation experiments in Monterey Bay using synthetic observations. The assimilation system is tested in a series of twin data experiments to assess its ability to fit assimilated and independent observations by controlling the initial conditions andor the external forcing while assimilating surface andor subsurface observations. In all strong and weak constraint experiments, the minimization of the cost function is done with both the gradient descent method in the control space and the representer method observation space. The accuracy of the forecasts following the analysis and the relevance of the retrieved forcing correction in the case of weak constraints are evaluated. It is shown that the assimilation system generally fits the assimilated and non-assimilated observations well in all experiments, yielding lower forecast errors.
- Physical and Dynamic Oceanography