Why is it in the news?

• The Indian National Centre for Ocean Information Services (INCOIS), an autonomous institution under the Union Ministry of Earth Sciences, has issued comprehensive swell wave advisories for the Andaman and Nicobar Islands, Lakshadweep, and coastal regions of Andhra Pradesh, Goa, Gujarat, Kerala, Maharashtra, Odisha, Tamil Nadu, West Bengal, Daman and Diu, and Puducherry.

About Swell waves

• Swell waves are long-wavelength ocean waves that travel far from their points of origin, often created by windstorms or powerful weather systems.
• Unlike locally generated sea waves, which are typically caused by nearby winds, swell waves form when air current systems transfer energy from the air to the water, making them more powerful. Due to this high energy, swell waves can travel vast distances and hit shores with significant force.
• According to the Indian National Centre for Ocean Information Services (INCOIS), swell waves organize into groups of similar heights and periods, traveling long distances without much change.
• The wave period, which is the time it takes for one wavelength to pass a point, is longer for swells with larger wavelengths, leading to faster and stronger waves.
• Swell waves lose less energy compared to shorter waves, allowing them to persist for days after formation. Forecasting the direction of swell waves is crucial, and meteorologists predict their movement using degrees indicating the swell’s origin.
• In India, INCOIS launched a swell surge forecast system in 2020 to provide warnings for coastal areas. Swell waves are known locally in Kerala as “Kallakkadal waves,” a term used by fishermen to describe sudden waves that cause flash floods. This term has now been officially recognized for scientific use by UNESCO.
• Although Kallakkadal waves may resemble tsunamis due to their sudden nature, the two are distinct. Swell surges result from weather phenomena, while tsunamis are usually triggered by earthquakes or tectonic activity.
• A 2016 study by INCOIS revealed that weather conditions in the Southern Indian Ocean, such as strong surface winds, contribute to the creation of long-period swells. These swells can propagate northward, leading to Kallakkadal events along the coastal regions of the North Indian Ocean.