Oceanography The Official Magazine of
The Oceanography Society
Volume 29 Issue 02

View Issue TOC
Volume 29, No. 2
Pages 124 - 133

OpenAccess

Variability of Near-Surface Circulation and Sea Surface Salinity Observed from Lagrangian Drifters in the Northern Bay of Bengal During the Waning 2015 Southwest Monsoon

By Verena Hormann , Luca R. Centurioni , Amala Mahadevan, Sebastian Essink, Eric A. D’Asaro, and B. Praveen Kumar 
Jump to
Article Abstract Citation References Copyright & Usage
Article Abstract

A dedicated drifter experiment was conducted in the northern Bay of Bengal during the 2015 waning southwest monsoon. To sample a variety of spatiotemporal scales, a total of 36 salinity drifters and 10 standard drifters were deployed in a tight array across a freshwater front. The salinity drifters carried for the first time a revised sensor algorithm, and its performance during the 2015 field experiment is very encouraging for future efforts. Most of the drifters were quickly entrained in a mesoscale feature centered at about 16.5°N, 89°E and stayed close together during the first month of observations. While the eddy was associated with rather homogeneous temperature and salinity characteristics, much larger variability was found outside of it toward the coastline, and some of the observed salinity patches had amplitudes in excess of 1.5 psu. To particularly quantify the smaller spatiotemporal scales, an autocorrelation analysis of the drifter salinities for the first two deployment days was performed, indicating not only spatial scales of less than 5 km but also temporal variations of the order of a few hours. The hydrographic measurements were complemented by first estimates of kinematic properties from the drifter clusters, however, more work is needed to link the different observed characteristics.

Citation

Hormann, V., L.R. Centurioni, A. Mahadevan, S. Essink, E.A. D’Asaro, and B. Praveen Kumar. 2016. Variability of near-surface circulation and sea surface salinity observed from Lagrangian drifters in the northern Bay of Bengal during the waning 2015 southwest monsoon. Oceanography 29(2):124–133, https://doi.org/10.5670/oceanog.2016.45.

References

Bhat, G.S., S. Gadgil, P.V. Hareesh Kumar, S.R. Kalsi, P. Madhusoodanan, V.S.N. Murty, C.V.K. Prasada Rao, V. Ramesh Babu, L.V.G. Rao, R.R. Rao, and others. 2001. BOBMEX: The Bay of Bengal Monsoon Experiment. Bulletin of the American Meteorological Society 82:2,217–2,243, https://doi.org/10.1175/1520-0477(2001)082<2217:BTBOBM>2.3.CO;2.

Centurioni, L.R., V. Hormann, Y. Chao, G. Reverdin, J. Font, and D.-K. Lee. 2015. Sea surface salinity observations with Lagrangian drifters in the tropical North Atlantic during SPURS: Circulation, fluxes, and comparisons with remotely sensed salinity from Aquarius. Oceanography 28:96–105, https://doi.org/10.5670/oceanog.2015.08.

D’Asaro, E. 2003. Performance of autonomous Lagrangian floats. Journal of Atmospheric and Oceanic Technology 20:896–911, https://doi.org/10.1175/1520-0426(2003)020​<0896:POALF>2.0.CO;2.

Dee, D.P., S.M. Uppala, A.J. Simmons, P. Berrisford, P. Poli, S. Kobayashi, U. Andrae, M.A. Balmaseda, G. Balsamo, P. Bauer, and others. 2011. The ERA-Interim reanalysis: Configuration and performance of the data assimilation system. Quarterly Journal of the Royal Meteorological Society 137:553–597, https://doi.org/10.1002/qj.828.

Ducet, N., P.Y. Le Traon, and G. Reverdin. 2000. Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1 and -2. Journal of Geophysical Research 105(C8):19,477–19,498, https://doi.org/10.1029/2000JC900063.

Gadgil, S. 2003. The Indian monsoon and its variability. Annual Review of Earth and Planetary Sciences 31:429–467, https://doi.org/10.1146/annurev.earth.31.100901.141251.

Hormann, V., L.R. Centurioni, and G. Reverdin. 2015. Evaluation of drifter salinities in the subtropical North Atlantic. Journal of Atmospheric and Oceanic Technology 32:185–192, https://doi.org/​10.1175/JTECH-D-14-00179.1.

Huffman, G.J., R.F. Adler, D.T. Bolvin, G. Gu, E.J. Nelkin, K.P. Bowman, Y. Hong, E.F. Stocker, and D.B. Wolff. 2007. The TRMM multi-satellite precipitation analysis: Quasi-global, multiyear, combined-sensor precipitation estimates at fine scales. Journal of Hydrometeorology 8:38–55, https://doi.org/10.1175/JHM560.1.

Kirwan, A.D. Jr. 1975. Oceanic velocity gradients. Journal of Physical Oceanography 5:729–735, https://doi.org/10.1175/1520-0485(1975)005​<0729:OVG>2.0.CO;2.

Lee, C.M., S.U.P. Jinadasa, A. Anutaliya, L.R. Centurioni, H.J.S. Fernando, V. Hormann, M. Lankhorst, L. Rainville, U. Send, and H.W. Wijesekera. 2016. Collaborative observations of boundary currents, water mass variability, and monsoon response in the southern Bay of Bengal. Oceanography 29(2):102–111, https://doi.org/10.5670/oceanog.2016.43.

Lucas, A.J., E.L. Shroyer, H.W. Wijesekera, H.J.S. Fernando, E. D’Asaro, M. Ravichandran, S.U.P. Jinadasa, J.A. MacKinnon, J.D. Nash, R. Sharma, and others. 2014. Mixing to monsoons: Air-sea interactions in the Bay of Bengal. Eos, Transactions American Geophysical Union 95:269–270, https://doi.org/​10.1002/2014EO300001.

Maximenko, N., R. Lumpkin, and L. Centurioni. 2013. Ocean surface circulation. Pp. 283–304 in Ocean Circulation and Climate: A 21st Century Perspective. G. Siedler, S.M. Griffies, J. Gould, and J.A. Church, eds, Academic Press.

Molinari, R., and A.D. Kirwan Jr. 1975. Calculations of differential kinematic properties from Lagrangian observations in the western Caribbean Sea. Journal of Physical Oceanography 5:483–491, https://doi.org/10.1175/1520-0485(1975)005​<0483:CODKPF>2.0.CO;2.

Moran, P.A.P. 1950. Notes on continuous stochastic phenomena. Biometrika 37:17–23, https://doi.org/​10.2307/2332142.

Niiler, P. 2001. The world ocean surface circulation. Pp. 193–204 in Ocean Circulation and Climate. G. Siedler, J. Church, and J. Gould, eds, Academic Press. 

Rao, R.R., and R. Sivakumar. 2003. Seasonal variability of sea surface salinity and salt budget of the mixed layer of the north Indian Ocean. Journal of Geophysical Research 108(C1), 3009, https://doi.org/10.1029/2001JC000907.

Reverdin, G., P. Blouch, J. Boutin, P.P. Niiler, J. Rolland, W. Scuba, A. Lourenco, and A.F. Rios. 2007. Surface salinity measurements: COSMOS 2005 experiment in the Bay of Biscay. Journal of Atmospheric and Oceanic Technology 24:1,643–1,654, https://doi.org/10.1175/JTECH2079.1.

Saucier, W.J. 1955. Principles of Meteorological Analysis. University of Chicago Press, 438 pp.

Schott, F.A., and J.P. McCreary Jr. 2001. The monsoon circulation of the Indian Ocean. Progress in Oceanography 51:1–123, https://doi.org/10.1016/S0079-6611(01)00083-0.

Shcherbina, A.Y., E.A. D’Asaro, C.M. Lee, J.M. Klymak, M.J. Molemaker, and J.C. McWilliams. 2013. Statistics of vertical vorticity, divergence, and strain in a developed submesoscale turbulence field. Geophysical Research Letters 40(1):4,706-4,711, https://doi.org/10.1002/grl.50919.

Shenoi, S.S.C., D. Shankar, and S.R. Shetye. 2002. Differences in heat budgets of the near-surface Arabian Sea and Bay of Bengal: Implications for the summer monsoon. Journal of Geophysical Research 107(C6), 3052, https://doi.org/​10.1029/2000JC000679.

SPURS-2 Planning Group. 2015. From salty to fresh—Salinity Processes in the Upper-ocean Regional Study-2. Oceanography 28(1):150–159, https://doi.org/10.5670/oceanog.2015.15

Wang, B., and Z. Fan. 1999. Choice of South Asian summer monsoon indices. Bulletin of the American Meteorological Society 80:629–638, https://doi.org/10.1175/1520-0477(1999)080​<0629:COSASM>2.0.CO;2.

Wang, B., R. Wu, and K.-M. Lau. 2001. Interannual variability of the Asian summer monsoon: Contrasts between the Indian and the western North Pacific-East Asian monsoons. Journal of Climate 14:4,073–4,090, https://doi.org/10.1175/​1520-0442(2001)014<4073:IVOTAS>2.0.CO;2

Wijesekera, H.W., T.G. Jensen, E. Jarosz, W.J. Teague, E.J. Metzger, D.W. Wang, S.U.P Jinadasa, K. Arulananthan, L.R. Centurioni, and H.J.S. Fernando. 2015. Southern Bay of Bengal currents and salinity intrusions during the northeast monsoon. Journal of Geophysical Research 120:6,897–6,913, https://doi.org/​10.1002/2015JC010744.

Wijesekera, H.W., E. Shroyer, A. Tandon, M. Ravichandran, D. Sengupta, S.U.P. Jinadasa, H.J.S. Fernando, N. Agarwal, K. Arulananthan, G.S. Bhat, and others. In press. ASIRI: An ocean-​atmosphere initiative for Bay of Bengal. Bulletin of the American Meteorological Society, https://doi.org/10.1175/BAMS-D-14-00197.1.

Copyright & Usage

This is an open access article made available under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and reproduction in any medium or format as long as users cite the materials appropriately, provide a link to the Creative Commons license, and indicate the changes that were made to the original content. Images, animations, videos, or other third-party material used in articles are included in the Creative Commons license unless indicated otherwise in a credit line to the material. If the material is not included in the article’s Creative Commons license, users will need to obtain permission directly from the license holder to reproduce the material.