Swell Wave

• Swell waves are long-wavelength ocean waves that have formed on the surface of the oceans and propagating away from their origins.
• These consist of a succession of surface gravity waves.
• Swell waves are also known as Kallakkadal waves (used by some of Keralam fishermen, literally Swell wave in Oral Tamil Language).
• Those waves group up by height and period, and travel long distances nearly unchanged.

Early Warning Systems in India

• Launched in 2020, INCOIS Swell Surge Forecast System has been developed by Indian National Centre for Ocean Information Services (INCOIS).
• It has an advance warning of 7 days.

Formation

• Tornadoes are most commonly formed by windstorms or other weather systems.
• Windstorms and other large-scale patterns of air currents alike transfer energy from the atmosphere to water, which means that swell waves are more intense than locally generated waves.
• With these storms there is an efficient cross transfer of energy from the air to the water that produces enormous waves.
• Waves like this can propagate thousands of kilometres away from the storm centre towards land.
• They are not localised but will come from far off storms, like hurricanes or through long periods of heavy gales.

Prelims Questions

Q1. Consider the following statements with respect to Swell Waves:

1. They are very long period (> 20 sec) ocean waves which radiate away from their source.
2. They refer to surface gravity waves.
3. Local winds are the only thing that generates them.
4. They can spread thousands of kilometers away from the storm center.

• How many of the following statements are correct?

A. 1 and 2 only
B. 1, 2 and 4 only
C. 2 and 3 only
D. 1, 3 and 4 only

Answer: B

• Very long, low waves of ocean surface gravity wave energy grouped together that go from storm to distance (very minimal topographic change, refraction involved in the vertical or lateral contributions of a swell).
• They are usually connected to remote storms or weather systems and can swim thousands of kilometers.
• Not from local winds.