Abstract
We conducted four-dimensional variational (4D-Var) data assimilation system in the Regional Ocean Modeling System (ROMS) in the Osaka Bay and modified the adjoint model to avoid numerical instability near narrow straits. While sequential assimilations with twenty-four 1-hour assimilation windows, the previous adjoint model assimilation made blowing up in 19-hour assimilation window, but the modified adjoint model was carried out stably over twenty-four windows. In addition, both models of RMSEs indicated almost the same values until 18-hour window. One 24-hour, two 12-hour, four 6-hour and twenty-four 1-hour assimilations are performed with modified model. The 24- or 12-hour window showed large RMSEs of sea surface temperature between the model and observations. The variation of salinity RMSEs was small. There are still substantial challenges we have to set up configurations of background error covariance.
