A case study of the genesis of a monsoon low and the thermal structure of the upper northern Bay of Bengal during monex-79

Abstract

The observed day to day variability in the thermal structure of the top 200 m water column at two stationary positions separated by a distance of about 440 km along 89 degrees E over the head of Bay of Bengal is studied with the aid of time series measurements of surface marine meteorological and Nansen Cast data collected during MONEX-79 experiment. The seasonal monsoon trough strengthened and gradually extended into the head Bay leading to the formation of a low pressure area during the period of study which subsequently deepened into depression. The cyclone heat potential registered a gradual increase at the northern location. Surface heat budget estimates are made to account the observed cooling of the sea surface and the deepening of the surface mixed layer. The observed vertical displacement in the thermocline does not appear to have been influenced by the prevailing surface wind stress curl. The spatial differences between the northern and southern locations are highlighted in terms of stronger stratification observed below the mixed layer at the northern location on account of its proximity to the mouth of the river Ganges, where abundant amount of fresh water discharge takes place