Assimilation of satellite and glider data in the Monterey Bay and Hawaiian regions using the Navy Coastal Ocean Model 4DVAR

A 4DVAR data assimilation system has recently been developed for the Navy Coastal Ocean Model (NCOM) and has been demonstrated using real ocean observations in this study. The NCOM-4DVAR is formulated for weak-constraint data assimilation based on the in-direct representer method. In this study, satellite data consisting of sea surface temperatures (SSTs) and sea surface height anomalies (SSHAs), as well as in-situ data from Airborne eXpendable BathyThermographs (AXBTs), ARGO floats, and gliders is used to derive optimal corrections to the ocean model background and surface forcing provided by the atmospheric model. Two regional domains have been selected for this study: the first consists of the waters adjacent to Monterey Bay, California during the AOSN-II experiment and the second in a region surrounding Hawaii during the RIMPAC08 experiment. It is shown that the NCOM-4DVAR can correct the model solution via control of the initial conditions and model error terms and produce an improved forecast as a result. Also the NCOM-4DVAR can produce optimal corrections to the atmospheric forcing based on ocean data. These corrections alone can be applied to the specified surface forcing to produce an improved ocean forecast.