Internal Tides in the Coastal Waters of NE Arabian Sea: Observations and Simulations

Time series of temperature and salinity collected from a station in the NE Arabian Sea during March, April, May, October, and November was utilized to explain the behavior of internal tides. Analysis revealed the existence of semi-diurnal internal tides and high frequency (HF) internal waves (IW). It was observed that the amplitudes of HF IWs were determined by the degree of stratification in the thermocline. Corresponding to an increase in the density gradient in thermocline (0.016 kg/m4 in April to 0.14 kg/m4 in October), the temperature fluctuations due to internal tides increased from <0.2°C to >1.5°C, respectively. Brunt-Vaiisala frequency also showed similar variations (∼10 cph to 22 cph). Within the thermocline, semi-diurnal internal tides caused fluctuations of >10m in the isotherm depths. A linear regression equation was fitted to parameterize the amplitude of HF IWs and its upper frequency limit in terms of thermocline gradient. The IW and one-dimensional models simulated the presence of internal tides and diurnal cycling in the temperature field, respectively. Coupling of these models showed improvement in the simulation of temperature.

[1]  G. V. Reddy,et al.  Sub-surface temperature oscillations and associated flow in the western Bay of Bengal , 1985 .

[2]  D. Korteweg,et al.  XLI. On the change of form of long waves advancing in a rectangular canal, and on a new type of long stationary waves , 1895 .

[3]  A. Elliott,et al.  Internal Waves in the Clyde Sea , 2002 .

[4]  Antony K. Liu,et al.  The Sulu Sea Internal Soliton Experiment , 1985 .

[5]  Chris Garrett,et al.  Space-Time Scales of Internal Waves' A Progress Report , 1975 .

[6]  S. Thorpe.  Ocean variability and acoustic propagation , 1992 .

[7]  A. E. Gill.  Atmosphere-Ocean Dynamics , 1982 .

[8]  A. Osborne,et al.  Internal Solitons in the Andaman Sea , 1980, Science.

[9]  K. V. Sanilkumar,et al.  Shallow Water Internal Waves and Associated Acoustic Intensity Fluctuations , 2006 .

[10]  A. New,et al.  An intercomparison of internal solitary waves in the Bay of Biscay and resulting from Korteweg-de Vries-Type theory , 2000 .

[11]  William H. Press,et al.  Numerical Recipes: FORTRAN , 1988 .

[12]  P. Kumar,et al.  Response of coastal waters off Karwar to a deep depression , 1991 .

[13]  Chris Garrett,et al.  Space-Time scales of internal waves , 1972 .

[14]  M. K. Antony,et al.  On vertical velocity fluctuations and internal tides in an upwelling region off the west coast of India , 1990 .

[15]  Robert Pinkel,et al.  Diurnal cycling: observations and models of the upper-ocean response to diurnal heating, cooling, and wind mixing. Technical report , 1986 .

[16]  S. Pond,et al.  Introductory Dynamical Oceanography , 1983 .

[17]  D. Korteweg,et al.  On the change of form of long waves advancing in a rectangular canal, and on a new type of long stationary waves , 2011 .

[18]  T. Pradeep Kumar,et al.  Observations on the relationship between scattering layer and mixed layer , 2005 .