SWELL WAVES - GEOGRAPHY
News: Swell waves likely to hit
several coastal areas
What's in the news?
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The Indian National Centre for Ocean Information
Services (INCOIS) forecasted that
high sea waves/ swell waves might hit both the west and east coasts of India
and Lakshadweep and A&N Islands between May 4 and 5.
Swell Waves:
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These waves are formed by an ocean swell, hence the name swell surge.
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Ocean swells occur not due to the local winds, but
rather due to distant storms like
hurricanes or even long periods of fierce gale winds.
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During such storms, huge energy transfer takes place from the air into the water,
leading to the formation of very high waves.
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These swell waves can travel thousands of kilometres from the storm centre until they
strike shore.
Swell Surge Forecast
System:
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To forecast swell waves, INCOIS launched the Swell Surge Forecast System in 2020 which can
give warning seven days in advance.
Vulnerable Regions for
Swell Waves in India:
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Usually, states like Kerala witness swell waves as a result of strong winds in the
southern part of the Indian Ocean.
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In March 2024, swell waves led to flooding in
several areas of Kerala - the worst affected were Alappuzha, Kollam, and
Thiruvananthapuram districts. Such flooding events are called Kallakkadal in
Kerala.
Difference Between Swell
Waves and Tsunamis:
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Unlike swell waves, a tsunami is a series of enormous waves created by an underwater
disturbance usually associated with earthquakes occurring below or near the
ocean.
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Tsunamis are around 10 times faster than swell waves. Although both swell waves and tsunamis slow down near the coast, the
latter hit land at 30–50 km/h.
Go back to basics:
Kallakkadal:
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‘Kallakkadal’ is a colloquial term used by Kerala
fishermen to refer to flash flooding
events.
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In Malayalam, Kallan means thief or mischievous one
and Kadal means sea.
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Fishermen use the term ‘Kalla Kadal’ to refer to
the unusual occurrence of high swell
waves during good weather.
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According to weather experts, the phenomenon is
triggered by storms as far away as the Antarctic region.
Features:
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Kallakkadal are caused by meteorological conditions in the Southern Ocean, south of 30°S.
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After travelling thousands of kilometres across the
ocean basin, the swell intensifies when it encounters a coastal current, a
phenomenon known as remote forcing.
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'Kalla Kadal' usually occurs along the southern
coast of India, mainly during the pre-monsoon period, in April and May during clear weather conditions.
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In 2012, UNESCO
formally accepted the term for scientific use.