Monsoon and Salinity Variation in Bay of Bengal

Using satellite data, we have characterized the influence of monsoon on the variation of surface salinity in the Bay of Bengal (BB). In the north, discharge from the Ganges-Brahmautra river, which originate in part from monsoon rainfall over land, dominates the salinity variation. In the south, salinity advection to and from the Arabian Sea (AS) coincides with the change of summer monsoon. We are examining whether surface salinity together with temperature influence the onset time of summer monsoon.The hottest and driest weeks over much of the India Subcontinent are found just before the summer monsoon onsets. We found that the pre-monsoon droughts and heat waves occur in the short periods when moisture advected out to BB is ahead of the input from AS. The onsets of southwest monsoon winds start in the BB and suck moisture out from the subcontinent earlier than the onsets in Arabian Sea. The phase difference of monsoon onsets in AS and BB are related the time difference of the peaks of sea surface temperature and surface salinity in AS and BB. These pre-monsoon drought and heat-waves on land cause economic and agricultural disasters besides human suffering and loss of life. The regional cause may lies in the ocean.