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


Affiliations
1 Space Applications Centre, Oceanic Sciences Division, Ahmedabad 380 058, India
2 Department of Meteorology and Oceanography, Andhra University, Visakhapatnam 530 003, India
 

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.

Keywords

Freshwater Content, Sea Surface Salinity, Seasonal Variability, Upper Ocean Region.
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  • Sengupta, D., Bharath Raj, G. N. and Shenoi, S. S. C., Surface freshwater from Bay of Bengal runoff and Indonesian Through-flow in the tropical Indian Ocean. Geophys. Res. Lett., 2006, 33, L22609; doi:10.1029/2006GL027573.

  • Perigaud, C., McCreary, J. P. and Zhang, K. Q., Impact of inter-annual rainfall anomalies on Indian Ocean salinity and temperature variability. J. Geophys. Res., 2003, 108, 3319; doi:10.1029/2002JC001699.

  • Rao, R. R. and Sivakumar, R., Seasonal variability of sea surface salinity and salt budget of the mixed layer of the north Indian Ocean. J. Geophys. Res., 2003, 108, 3009; doi:10.1029/2001JC000907.

  • Sharma, R., Mankad, B., Agarwal, N., Kumar, R. and Basu, S., An assessment of two different satellite-derived precipitation products in relation to simulation of sea surface salinity in the tropical Indian Ocean, J. Geophys. Res., 2012, 117, C07001; doi:10.1029/2012JC008078.

  • Gadgil, S., Joseph, P. V. and Joshi, N. V., Ocean–atmosphere coupling over monsoon regions. Nature 1984, 312, 141–143.

  • Neetu, S. et al., Influence of upper ocean stratification on tropical cyclone-induced surface cooling in the Bay of Bengal. J. Geophys. Res., 2012, 117, C12020, 3315–3329; doi:10.1029/2012JC008433/

  • Pant, V., Girishkumar, M. S., Udaya Bhaskar, T. V. S., Ravichandran, M., Papa, F. and Thangaprakash, V. P., Observed interannual variability of near-surface salinity in the Bay of Bengal, J. Geophys. Res., 2015, 120; doi:10.1002/2014JC010340.

  • Akhil, V. P. et al., A modeling study of the processes of surface salinity seasonal cycle in the Bay of Bengal. J. Geophys. Res., 2014, 119, 3926–3947; doi:10.1002/2013JC009632.

  • Wiffels, S. E., Schmitt, R. W., Bryden, H. R. and Stigebrandt, A., Transport of freshwater by Oceans. J. Phys. Oceanogr., 1992, 22, 155–162.

  • Behara, A. and Vinayachandran, P. N., An OGCM study of the impact of rain and river water forcing on the Bay of Bengal. J. Geophys. Res., 2016, 121, 2425–2446; doi:10.1002/2015JC011325.

  • Chakraborty, A., Sharma, R., Kumar, R. and Basu, S., A SEEK filter assimilation of sea surface salinity from Aquarius in an OGCM: implication for surface dynamics and thermohaline structure. J. Geophys. Res., 2014, 119, 4777–4796; doi:10.1002/2014JC009984.

  • Chakraborty, A., Sharma, R., Kumar, R. and Basu, S., Joint assimilation of Aquarius-derived sea surface salinity and AVHRR-derived sea surface temperature in an ocean general circulation model using SEEK filter: implication for mixed layer depth and barrier layer thickness. J. Geophys. Res., 2015, 120, 6927–6942; doi:10.1002/2015JC010934.

  • Blumberrg, A. F. and Mellor, G. L., A description of a three-dimensional coastal ocean circulation model. In Three Dimensional Coastal Ocean Models (ed. Heaps, N. S.), Amer. Geophys. Union, Washington, DC, USA, 1987, pp. 1–16; doi:10.1029/CO004P0001.

  • Mellor, G. L. and Yamada, T., Development of a turbulence closure model for geophysical fluid problems. Rev. Geophys. Space Phys., 1982, 20, 851–875.

  • Camerlengo, A. L. and O’Brien, J. J., Open boundary conditions in rotating fluids. J. Comput. Phys., 1980, 35, 12–35.

  • Santoki, M., Ratheesh, S., Sharma, R., Joshipura, K. N. and Basu, S, Assimilation of drifter data in a circulation model of the Indian Ocean. IEEE Geosci. Remote Sensing. Lett., 2012, 9, 100–103.

  • Santoki, M., George, S., Sharma, R., Joshipura, K. N. and Basu, S., Assimilation of satellite-derived ocean surface current in an Indian Ocean circulation model. Remote Sensing Lett., 2013, 4, 475–484.

  • Ratheesh, S., Sharma, R. and Basu, S., Projection-based assimilation of satellite-derived surface data in an Indian Ocean circulation model. Mar. Geod., 2012, 35, 175–187.

  • Ratheesh. S., Sharma, R. and Basu, S., An EnOI assimilation of satellite data in an Indian Ocean circulation model. IEEE Trans. Geosci. Remote Sensing, 2014, 52, 4106–4111.

  • Oke, P. R., Brassington, G. B., Griffin, D. A. and Schiller, A., Ocean data assimilation: a case for ensemble optimal interpolation. Aust. Meteorol. Ocean J., 2010, 59, 67–76.

  • Wan, L., Bertino, L. and Zhu, J., Assimilating altimetry data into a HYCOM model of the Pacific: ensemble optimal interpolation versus ensemble Kalman filter. J. Atmos. Ocean. Technol., 2010, 27, 753–776.

  • Ratheesh. S., Sharma, R., Prasad, K. V. S. R. and Basu, S., Impact of SARAL/AltiKa-derived sea level anomaly in a data assimilative ocean prediction system for the Indian Ocean. Mar. Geod., 2015, 38, 354–364; doi:10.1080/01490419.2014.988833.

  • Levine, M., Lagerloef, G. S. E., Colomb, R., Yueh, S. and Pellerano, F., Aquarius: an instrument to monitor sea surface salinity from space. IEEE Trans. Geosci. Remote Sensing, 2007, 45, 2040–2050.

  • Ratheesh, S., Sharma, R., Sikhakolli, R., Kumar, R. and Basu, S., Assessing sea surface salinity derived by Aquarius in the Indian Ocean. IEEE Geosci. Remote Sensing Lett., 2014, 11, 719–722.

  • Tang, W., Yueh, S. H., Fore, A. G. and Hayashi, A., Validation of Aquarius sea surface salinity with in situ measurements from Argo floats and moored buoys. J. Geophys. Res., 2014, 119, 6171–6189; doi:10.1002/2014JC010101.

  • Kohl, A. and Serra, N., Causes of decadal changes of the freshwater content in the Arctic Ocean. J. Climate, 2014, 27(9), 3461–3475.

  • Stammer, D. et al., Volume, heat, and freshwater transports of the global ocean circulation 1993–2000, estimated from a general circulation model constrained by World Ocean Circulation Experiment (WOCE) data. J. Geophys. Res., 2003, 108(C1), 3007; doi:10.1029/2001JC001115.

  • Han, W., McCreary J. P. and Kohler, K. E., Influence of precipitation minus evaporation and Bay of Bengal rivers on dynamics, thermodynamics and mixed layer physics in the upper Indian Ocean. J. Geophys. Res., 2001, 106(C4), 6895–6916.

  • Thadathil, P., Muraleedharan, P. M., Rao, R. R., Somayajulu, Y. K., Reddy, G. V. and Revichandran, C., Observed seasonal variability of barrier layer in the Bay of Bengal. J. Geophys. Res., 2007, 112, C02009; doi:10.1029/2006JC003651.

  • Prasad, T. G., Annual and seasonal mean buoyancy fluxes for the tropical Indian Ocean. Curr. Sci., 1997, 73(8), 667–674.

  • Mahadevan, A., Spiro Jaeger, G., Freilich, M., Omand, M., Shroyer, E. L. and Sengupta, D., Freshwater in the Bay of Bengal: its fate and role in air–sea heat exchange. Oceanography, 2016, 29(2), 72–81; http://dx.doi.org/10.5670/oceanog.2016.40.

  • Rao, S. A. et al., Modulation of SST, SSS over northern Bay of Bengal on ISO time scale. J. Geophys. Res., 2011, 116, C09026; doi:10.1029/2010JC006804.

  • Chaitanya, A. V. S. et al., Observed year-to-year sea surface Salinity variability in the Bay of Bengal during the 2009–2014 period. Ocean Dyn., 2015, 65, 173–186.

  • Yu, L., A global relationship between the ocean water cycle and near-surface salinity. J. Geophys. Res., 2011, 116, C10025; doi:10.1029/2010JC006937.


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

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Authors

Smitha Ratheesh
Space Applications Centre, Oceanic Sciences Division, Ahmedabad 380 058, India
Rashmi Sharma
Space Applications Centre, Oceanic Sciences Division, Ahmedabad 380 058, India
K. V. S. R. Prasad
Department of Meteorology and Oceanography, Andhra University, Visakhapatnam 530 003, India
Neeraj Agarwal
Space Applications Centre, Oceanic Sciences Division, Ahmedabad 380 058, India
Rashmi Sharma
Space Applications Centre, Oceanic Sciences Division, Ahmedabad 380 058, India
V. S. R. Prasad
Department of Meteorology and Oceanography, Andhra University, Visakhapatnam 530 003, India

Abstract


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.

Keywords


Freshwater Content, Sea Surface Salinity, Seasonal Variability, Upper Ocean Region.

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DOI: https://doi.org/10.18520/cs%2Fv115%2Fi1%2F99-107