THE EFFECT OF MONSOON ON THE BAY OF BENGAL BASED ON A HYDRODYNAMIC MODEL

Understanding hydrodynamics in Bay of Bengal (BoB) is crucial because of its connectivity to local extreme weather, ocean fronts, pollutions, and fishing activities. This study aims to describe the hydrodynamics of BoB, including the gyre and the temperature-salinity profile during the monsoon. The research was conducted based on simulating a three-dimensional numerical model, i.e., the HAMburg Shelf Ocean Model (HAMSOM). The model is forced by the tides and meteorological forcing obtained from NCEP/NCAR Reanalysis, which consists of sea level pressure, cloud cover, precipitation, relative humidity, air temperature, zonal and meridional wind. The results showed that the hydrodynamic model (HAMSOM) is quite realistic, according to The Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) and previous research. OSTIA is a product of a combination of in-situ SST data (Sea Surface Temperature) with reasonably high accuracy. According to the results (HAMSOM), in February (Northeast monsoon), the sea surface currents of BoB are dominated by the poleward East India Coastal Current (EICC) and anticyclone gyres, while the bottom currents are dominated by the reversing EICC originating from near the Andaman Island (more than 300 meters). In this period, atmospheric conditions and sea surface currents support a cold SST and deep mixed layer depth in BoB (reaching 125 meters). In August, the southwest wind is very strong, causing the eastward currents and more gyre in BoB. Also, SST is relatively warm, so the temperature in a vertical direction is more stratified. Compared to the other parts, stratification is very strong in the north of BoB. More stratification at the sea surface is induced by the high precipitation and high SST in August or summer periods. Meanwhile, the stratification of temperature spatially varies due to the gyre and the current circulation. According to the result, it is known that the atmospheric variability of BoB determines the strength of the gyre, coastal currents, and ocean stratification.