Mixed Layer Budget Terms on Acoustic Propagation A Study based on the Butterfly Track Experiment in the South Eastern Arabian Sea
A butterfly type of repeat track cruise was carried out in the South Eastern Arabian Sea (off Minicoy) onboard INS Sagardhwani during July 2016 to Aug 2016. We have also made use of the data from OMNI buoy, AD09, which is about 6 km close to the centre station of butterfly track. Air sea flux, the horizontal current data from AD09 and the time series data collected from the butterfly experiment were analyzed to compute the mixed layer heat and salt budget. The short-term thermo-haline variability off Minicoy, relative contribution of heat/salt budget terms in MLD and its effects on acoustic propagation are addressed in this paper. In this study, we found that most dominating term in the mixed layer heat budget estimation is net surface heat flux followed by the advective terms. However the salinity in the mixed layer is dominated by the contribution of buoyancy mixing due to night time evaporative cooling. During the calm, sunny day, the so-called afternoon effect due to the diurnal heating restricts the sonar range. But during the windy day, the wind/wave mixing prevents the warming of the surface layer which in turn enhances the sonar range. Similarly, the night time cooling also enhance the acoustic propagation range. The presence of Arabian Sea High Salinity Watermass in the surface layer also enhances the acoustic propagation.
Helber, R.W.; Barron, C.N.; Carnes, M.R. & Zingarelli, R. A. Evaluating the sonic layer depth relative to the mixed layer depth. J. Geophys. Res., 2008, 113, C07033.
Urick, R.J. In Principles of Underwater Sound, 3rd ed. Peninsula, Los Altos, California, 1983, pp.423.
Rao, R.R. & Sivakumar, R. Seasonal variability of near-surface thermal structure and
heat budget of the mixed layer of the tropical Indian Ocean from a new global ocean temperature climatology. J. Geophys. Res., 2000, 105(C1), 995–1016.
Sengupta, D.; Ray, P.K. & Bhat, G.S. Spring warming of the eastern Arabian Sea and Bay of Bengal from buoy data. Geophys. Res. Lett., 2002, 29(15).
Shenoi S.S.C.; Shankar, D. & Shetye, S.R. Differences in heat budgets of the near-surface Arabian Sea and Bay of Bengal: Implications for the summer monsoon. J. Geophys. Res., 2002, 107(C6).
Prasad, T.G. A comparison of mixed-layer dynamics between the Arabian Sea and Bay of Bengal: One-dimensional model results. J. Geophys. Res., 2004, 109, C03035,
Boyer Montégut, C.; Vialard, J.; Shenoi, S.S.C.; Shankar, D.; Durand, F.; Ethé, C. & Madec, G. Simulated seasonal and inter annual variability of mixed layer heat budget in the northern Indian Ocean. J. Clim., 2007, 20, 3249-3268.
Chowdary, J.S.; Parekh, A.; Ojha, S. & Gnanaseelan, C. Role of upper ocean processes in the seasonal SST evolution over tropical Indian Ocean in climate forecasting system. Climate Dynam., 2015, 45(2), 387–405.
Rao, R.R. & Sivakumar, R. On the possible mechanism of the evolution of a mini-warm pool during the pre-monsoon season and the onset vortex in the Southeastern Arabian Sea. Q.J.R. Meteorol. Soc., 1999, 125, 787-809.
Rao, R.R. & 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(C1), 3009.
Nyadjro, E.S.; Subrahmanyam, B.; Murty, V.S.N. & Shriver, J.F. The role of salinity on the dynamics of the Arabian Sea Mini Warm Pool. J. Geophys. Res., 2012, 117, C09002.
F F arrar, J.T.; Rainville, L.; Plueddemann, A.J.; Kessler, W.S.; Lee, C.; Hodges, B.A.; Schmitt, R.W.; Edson, J.B.; Riser, S.C.; Eriksen, C.C. & Fratantoni, D.M. Salinity and temperature balances at the SPURS central mooring during fall and winter. Oceanography, 2015, 28(1), 56–65.
Venkatesan, R., Shamji, V. R., Latha, G., Mathew, S., Rao, R. R., Muthiah, A. & Atmanand, M. A. In situ ocean subsurface time series measurements from OMNI buoy network in the Bay of Bengal. Curr. Sci., 2013, 104(9), 1166–1177.
Sengupta, D.; Parampil, S.R.; Bhat, G.S.; Murty, V.S.N.; Babu, V. Ramesh; Sudhakar, T.; Premkumar, K. & Pradhan, Y. Warm pool thermodynamics from the Arabian Sea Monsoon Experiment (ARMEX). J. Geophys. Res., 2008, 113, C1008.
Swenson, M. S. & Hansen, D.V. Tropical pacific ocean mixed layer heat budget: The pacific cold tongue. J. Phys. Oceanogr., 1999, 29, 69–81.
Kurian, J. & P. N. Vinayachandran. Mechanisms of formation of the Arabian Sea mini warm pool in a high-resolution ocean general circulation model. J. Geophys. Res., 2007, 112, C05009.
Delcroix, T. & C. Henin. Seasonal and Interannual variations of the sea surface salinity in the tropical Pacific Ocean. J. Geophys . Res., 1991, 96, 22135 –22150,
F F oltz, G. R. & M. J. McPhaden. Seasonal mixed layer salinity balance of the tropical North Atlantic Ocean. J. Geophys. Res., 2008, 113, C02013,
Parampil, S.R., A. Gera, M. Ravichandran, & D. Sengupta. Intraseasonal response of mixed layer temperature and salinity in the Bay of Bengal to heat and freshwater flux. J. Geophys. Res., 2010, 115, C05002,
Morel, A. Optical modeling of the upper ocean in relation to its biogenous matter content (case I waters). J. Geophys. Res., 1988, 93(1), 652–665.
Kumar, Satheesh S. A modifi ed numerical approach for leaky mode computation. Acta Acustica United Acustica, 2017, 103(5), 767-777.
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