Seasonal Behaviour of Upper Ocean Freshwater Content in the Bay of Bengal:Synergistic Approach Using Model and Satellite Data

Any Change In Precipitation, Evaporation And River Discharge, By Virtue Of Its Impact On The Distribution Of Ocean Salinity, Leaves Its Inevitable Signature On The Freshwater Content (fwc) In The Oceans. In This Study, Synergistic Use Of Satellite Data And Numerical Ocean Circulation Model Is Explored To Examine The Seasonality Of Fwc Of The Upper 30 M Water Column Of The Bay Of Bengal (bob). For This Purpose, First The Sea Surface Salinity (sss) From Aquarius Is Assimilated Into A Model Of The Indian Ocean. Strength Of Assimilation Is Judged By Comparing Simulated Sss With Satellite And Argo Datasets. An Overall Improvement Of 39% Is Observed In Sss Over Free Run Of The Model Without Data Assimilation. Next, The Focus Is Shifted To The Spatial And Temporal Variability Of Fwc Of The Upper 30 M Of Bob In Relation To The Different Components Of Freshwater Forcing. A Delay Of Three Months In The Peak Of Fwc Is Observed With Respect To The Peak Of Net Freshwater Influx For Bob As A Whole. However, The Nature Of The Response Of Fwc To The Total Freshwater Input Forcing In The Major River-dominated Regions Of Bob Is Different From That For The Whole Bob. The Relative Role Of River Influx In Controlling Fwc In These Regions Is Well Brought Out In The Study. For The Ganga–brahmaputra Region, River Run-off Is Observed To Be A Crucial Parameter In Regulating Fwc, Whereas For Both Irrawaddy River Region And Central Bob, Precipitation Dominates The Response. The Response Of Salinity In The Uppermost Part Of The Northern Bob To The Total Freshwater Input Is Much More Rapid Than In The Other Regions.