Application of the Navy Coastal Ocean Model 4DVAR for ocean data assimilation in the Okinawa Trough region

The recently developed 4DVAR for the Navy Coastal Ocean Model (NCOM-4DVAR) is applied to the Okinawa Trough region using both satellite and in-situ data. In this study, a weak constraint 4dvar is carried out to fit the ocean observations collected in this region. Given the ability of 4dvar to propagate information from the observation site along strong currents (flow dependence) and to other variables (cross-correlations) via the dynamics of the linearized model, the analysis and forecast will be examined in regions downstream from observation sites against withheld data in the downstream region. Also, variable types (i.e. temperature, salinity, or SSH) will be assimilated alone and the performance of the analysis and forecast for the other variables will be judged against the withheld data.