Context: Recently, swell waves inundated coastal areas in central and southern districts of Kerala.

• Due to a potentially deadly swell of waves hitting the coastal regions, scientists have recommended a complete stoppage of all recreational activities along the coast and beaches of numerous states on India's eastern and western coasts.

What is a Swell wave?

• A swell is the formation of long wavelength waves on the surface of the seas. These are composed of a series of surface gravity waves.

• The development of long wavelength waves on the ocean's surface is known as a swell. These are made up of several waves of surface gravity.

Formation

• These waves are caused by far-off storms like hurricanes or even extended periods of intense gale winds.

• During such storms, huge energy transfer takes place from the air into the water, leading to the formation of very high waves. Such waves can travel thousands of kilometres from the storm centre until they strike shore.

• In India, early warning systems like the Swell Surge Forecast System, which was introduced by the Indian National Centre for Ocean Information Services (INCOIS) in 2020, provide information about the formation of extremely high waves.

Features

• Swells have a narrower range of frequencies and directions than locally generated wind waves, because swell waves have dispersed from their generation area, have dissipated and therefore lost an amount of randomness, taking on a more defined shape and direction.

• These waves can propagate in directions that differ from the direction of the wind, in contrast to a wind sea.

• Their wavelengths may rarely exceed more than 150 m. Swell wavelength, also, varies from event to event. Occasionally, swells which are longer than 700 m occur as a result of the most severe storms.

• It occurs without precursors or any kind of local wind activity and as a result.

About Waves

• Waves are a surface disturbance in the ocean or sea that take the shape of a shifting swell or ridge.

• Unlike tides, which are caused by the moon, waves are caused by the transfer of energy from the wind to the sea.

• The wind causes friction on the sea's surface, which forms waves.