Internal Waves (IWs) are prominent features that undulate in the subsurface ocean in regions of well-defined density stratification. Their generation is influenced by bathymetry, atmospheric forcing, and internal tides which ultimately transport momentum and energy across long distances. IWs can propagate hundreds of kilometers, where most of their energy dissipates into turbulent mixing. The strength of IWs derives from the contrast of the subsurface density gradient where the strengthened stratification typically results in higher wave frequencies and faster phase speeds. A common type of IWs is the solitons or solitary waves, which are irregular and non-sinusoidal features at the sea surface. Solitary waves displace the thermocline and induce vertical circulation with reverberating effects to the sea surface roughness. More recent observations allow us to analyze surface effects of IWs through multi-parameter analysis by means of remote sensing techniques such as the Synthetic Aperture Radar (SAR) and Ocean Color Imagery.

Although IWs occur globally, they are most common within coastal or semi-enclosed regions where steep bathymetry results in nonlinear deformation of tidal currents. Profound solitary waves are in the Indian Ocean, specifically in the Andaman Sea, where IWs reach amplitudes greater than 60 m in height and can travel with speeds up to 2 m/s. The Andaman Sea is dominated by semi-diurnal tides year-round with greatest amplitudes during April–November, during which time IWs are particularly intense. Wind forcing alters hydrodynamic patterns of IWs through the air-sea interface especially during monsoon season. Seasonal monsoons, the Northeast (NE) monsoon, and the Southwest (SW) monsoon, provide episodic disturbances such as strong winds that can induce higher surface waves, increase precipitation, and deepen the thermocline/pycnocline. While there are studies on the tidal (semi-diurnal and diurnal) characteristics in the Bay of Bengal (BoB) and Andaman Sea using sea level data at coastal stations, observations and models, studies on IWs are limited to estuaries and coastal regions along the east coast of India. There are presently a few studies detecting the IWs using salinity in the BoB.

In this research, we used NASA's Soil Moisture Active Passive (SMAP) salinity to understand the relationship between freshwater dynamics and IWs. We used NASA's Estimating the Circulation and Climate of the Ocean (ECCO) project's 1/48° LLC4320 hourly simulations of salinity estimates during September 2011 – November 2012, and in situ hourly salinity observations from Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) moorings data and National Institute of Ocean Technology (NIOT) moorings data to better understand IW characteristics and propagation through salinity.