Indian National Centre for Ocean Information Services (INCOIS) here has stated that the high swell waves along the Indian coastline, which caused the sea to make inroads into the land in most coastal States by about 200 metres, have subsided and its warning has been confined to West Bengal coast on Thursday.
The Earth System Science Organisation (ESSO) working under the Ministry of Earth Sciences earlier was successful in giving three days’ advance warning to the coastal community about the swell surge. It was explained that a low pressure system formation on April 15 in the southern Indian Ocean off Africa, 9,000 km away from the Indian coast remained stationary for three days continuously with wave generation for around 1,600 square km.
This low pressure system named ‘Cut off Lows’ blocked the normal course of westerly winds present in the southern ocean during the period causing propagation of high swell waves towards Indian coasts. Satellite observations showed wind speed of about 26 metres per second in source area. Waves reached up to 15 metres high, explained INCOIS Director Satish C. Shenoi.
Precise modelling
“It differs from Tsunami as the waves surge happened due to the upper air circulation whereas during Tsunami waves are generated due to quake on the ocean bed,” he said. INCOIS has been the first institute in the Indian Ocean and Pacific region to forecast the surge waves precisely through its “numerical modelling” followed by data recording from its wave rider buoys and moored buoy devices deployed in the ocean, Head, Ocean Science & Information Services Group, INCOIS, T.M. Balakrishnan Nair said. Swell waves first hit Seychelles on April 20 and southern tip of India on April 21. Kerala fishermen call such flash flood phenomenon ‘Kallakkadal’ and this has been formally approved by the United Nations Educational, Scientific and Cultural Organization (UNESCO) in 2012.
Linked phenomenon
INCOIS research study (published recently in the Journal of Geophysical Research – Ocean) has established the link between North Indian Ocean high swell events and meteorological conditions in the Southern Ocean between Africa and Australia using a combination of ocean wave observations and numerical model simulations, said Dr. Nair.
The scientist, who was part of the research along with associates P.G. Remya, S. Vishnu, B Praveen Kumar and B, Rohith, said the study showed that ‘Kallakkadal’ events along the coasts can be effectively monitored and forecast at least two days in advance if the meteorological conditions are properly monitored.
