A Regional Coupled Model Study on the Circulation Features and Ocean State Reprenentations of Bay of Bengal Region

A Regional Coupled Model using COAWST (Coupled Ocean Atmospheric Wave Sediment Transport) modelling system is used to analyze the circulation and oceanic properties of the Bay of Bengal (BOB) region. BOB is a wind driven, highly active, seasonally varying complex system. The COAWST modelling system comprised of advanced numerical models such as Regional Ocean Modelling System (ROMS) as oceanic component and Weather Research and Forecasting Model (WRF) as atmospheric component. A two way coupling between ROMS and WRF is setup to transfer Sea Surface Temperature (SST) from ROMS to WRF and Sea surface stress and net heat flux from WRF to ROMS. Three simulations (WRF alone, ROMS alone, ROMS-WRF coupled) are performed to study the BOB region. Results are compared with remote observations as well as other available model results. Model results from the coupled run indicate improvement in surface current simulation with increased velocities. Air-Sea interactions are better captured with the coupled run, resulting in a decreased overall sea surface temperature with respect to standalone ROMS model run. In winter, along the northern bay, the coupling enhances cooling of the surface. Depth of 20 ̊C isotherm also varies (from ROMS alone simulation) with the inclusion of atmospheric feedback in the coupled model run. Even though the surface velocities are improved with feedback from atmospheric model, the circulations at 500 m depth and higher show no significant change in coupled run. Overall the coupled model simulations result in better representation of the oceanic state when compared to ROMS alone simulation for the BOB region.