The swell waves, without providing any signs in the local winds, at times cause severe flooding events along the east and west coasts of India. The phenomenon often causes destruction along the coast, with fishermen losing fishing gear and vessels due to sudden coastal flooding. Read here to learn more about them.
Swell Waves are Surface gravity waves on the ocean that are not growing or being sustained any longer by the wind.
Generated by the wind some distance away and now propagating freely across the ocean away from their area of generation, these waves can propagate in directions that differ from the direction of the wind, in contrast to a wind sea.
Kallakadal or Swell surges are flash flood events that take place without any prominent warnings or changes in local winds.
Swell waves or Swell surge
Swell waves, often simply referred to as swells, are a type of surface gravity wave that occurs in the open ocean and seas.
- Unlike waves generated by local winds (wind waves), swells are characterized by their smoother, more regular appearance and longer wavelengths.
- They are generated by distant weather systems and can travel thousands of miles from their origin, retaining energy over vast distances.
Formation of Swell Waves
- Generation: Swells begin as wind waves, which are generated by the wind blowing over the surface of the ocean. The energy transferred from the wind to the water creates waves.
- Growth: These waves can grow larger if the wind continues to blow steadily over a long distance (fetch) and a sufficient period.
- Propagation: Once the waves move out of the area influenced by the generating wind, they start to organize into sets of smoother, more uniform waves. The process of dispersion helps in sorting the waves according to their speed and wavelength, with longer waves moving faster and outpacing the shorter ones.
- Swell: The remaining organized, long-period waves that have travelled out of their generating area are known as swell waves. They can travel across entire ocean basins from their source to distant shores.
Characteristics of Swell Waves
- Long Wavelengths: Swells have longer wavelengths than wind waves, often ranging from 100 to 200 meters (330 to 660 feet), and sometimes even more.
- High Speeds: Their speed allows them to travel significant distances; swells can cross entire ocean basins.
- Smooth Appearance: Unlike choppy wind waves, swells have a smoother appearance with more rounded crests.
- Energy: Despite losing some energy during their journey, swells retain a significant amount of energy, which can impact coastlines far from their origin.
Impact of Swell Waves
- Surfing: Swells are essential for surfing, providing the consistent, large waves sought after by surfers. The quality of surf breaks is significantly influenced by the characteristics of incoming swells, such as their direction, period, and size.
- Coastal Erosion: Swell waves can contribute to coastal erosion, especially during storms when their energy is amplified.
- Navigation and Safety: For maritime navigation, understanding swells is crucial for the safety and efficiency of shipping and small craft operations.
- Energy Generation: Swell waves are a focus of research for renewable energy generation, where their consistent nature could be harnessed to produce electricity.
Swell waves vs Wind waves
Why in the news?
A low atmospheric pressure that formed in the South Atlantic Ocean on March 23 triggered swell waves, known as โKallakkadalโ locally, along the coastal areas of Thiruvananthapuram, Kollam, Alappuzha and Thrissur districts.
- The statement was issued by the Indian National Centre for Ocean Information Services (INCOIS), a Central government agency that issues weather warnings for fishermen in the country.
- As a result of the low-pressure area formed over the Atlantic Ocean moving into the Indian Ocean, high swell waves in the range of 11 m were formed, which finally reached the coast of Kerala and Lakshadweep, said the Kerala State Disaster Management Authority (KSDMA).
Kallakadal
The term Kallakkadal, used by local fishermen, is a combination of two Malayalam words, including Kallan and Kadal.
- Kallan means thief and Kadal means sea. In spoken language, these words were combined to mean ocean that arrives as a thief.
- These events are typically the result of distant storms or changes in atmospheric pressure, which generate large, powerful swell waves that travel across the ocean and impact the coast.
- The term has been brought into the spotlight due to such events causing unexpected flooding and damage along the coastal areas, even in the absence of local storm conditions.
Rogue waves, or freak waves as they are sometimes called, are massive and spontaneous ocean waves that can occur far out at sea or near coastlines.
- Unlike “kallakadal,” which is a regional term, rogue waves are a more broadly recognized phenomenon and have been observed and studied worldwide.
- They are notoriously unpredictable and can be extremely dangerous to ships and coastal structures due to their immense size and power.
- The phenomenon of “kallakadal” emphasizes the interconnectedness of global weather and ocean systems.
- Swells generated by distant meteorological events can travel vast distances across the ocean basins, affecting coastlines far from the source of the disturbance.
- This highlights the importance of global ocean monitoring systems and the need for comprehensive coastal management practices that take into account not only local weather and sea conditions but also distant events that could potentially cause significant impacts.
Conclusion
Swell waves play a significant role in the dynamics of the ocean and have profound impacts on human activities and the coastal environment. Their study is crucial in the fields of oceanography, marine planning, and coastal management.
Understanding the dynamics of swell waves, including events like “kallakadal,” is crucial for coastal communities, especially in terms of preparedness and mitigation strategies to minimize damage from such unexpected natural events.
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-Article by Swathi Satish
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