Response of the Bay of Bengal Circulation characteristics to the interannual forcing using Regional Ocean Modeling System (ROMS)

The objective of this work is to find the interannual forcing response to circulation dynamics of the Bay of Bengal in the time scale over the last two decades. We want to gain new insight on the interannual forcing particularly the surface wind reversal to the northward Western Boundary Current (WBC) and the southward East India Coastal Current (EICC) in the Bay of Bengal with the development of oceanic eddies. We set up the Regional Ocean Modeling Systems (ROMS) for the Bay of Bengal extended over 4°N to 24°N and 76°E to 100°E. The model has an average horizontal resolution of 10 km with 32 terrine following vertical levels. The initial and boundary condition is derived from the January values of the Mercator Ocean data from 2004. The model is forced with the inter-annual forcing from ECMWF Air-Sea fluxes. With the above mentioned model configuration an interannual simulation is carried out to study the interannual variation of the characteristics of the WBC and the EICC, and the associated basin scale gyre. We discuss the model performance and analyze the trends and variability of temperature and salinity over the basin for the period 2004-2010. We have also investigated the interannual variation of the occurrence, movement and lifecycle of the mesoscale eddies and their influences on the weakening and strengthening of boundary currents in the bay during the El-Nino/Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) years.