Hydro-meteorological impact on residual currents and salinity distribution at the Meghna Estuary of Bangladesh

Abstract

In this article, a 3D numerical model has been applied for the simulation of residual currents in the Meghna Estuary, situated at the northern Bay of Bengal. Relevant meteorological and hydrological data at the Meghna Estuary has been analyzed to identify the seasonal variation which has been employed as model input. Numerical investigations revealed that during the monsoon as well as winter periods a counterclockwise circulation exists in the estuary with a northward flow in the Sandwip Channel and another northward flow in the Shabazpur Channel. Numerical experiments suggest that tidal current is the primary forcing factor behind the northward flow through the Sandwip Channel. During the monsoon period, residual current in the northern Bay of Bengal may be occasionally dominated by strong South-West monsoon wind (average 4~5 m/s and maximum 20~30 m/s) which may create back water effects in the Meghna Estuary and alter the salinity distribution in the estuary. During winter (dry) season the counter clockwise circulation in the estuary exists but the circulation becomes weaker and it is not influenced by the weak north-easterly (1.5~3 m/s) wind. Thus, tidal current and Coriolis force were found to be the primary forcing factors that govern the residual circulation in the Meghna Estuary.