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Abstract Submission No. | ABS-2022-04-0332 |
Title of Abstract | Analysis of subsurface temperature deviation in OMNI buoy system due to extreme mooring movement during super cyclonic storm Amphan |
Authors | Venkatesan R., Biswajit Haldar*, Senthilkumar P., Jossia Joseph K., Arul Muthiah M., Kesavakumar B |
Organisation | National Institute of Ocean Technology |
Address | Flat-E, Anuradha Flat, Santhosh Street, VGP Shanti Nagar, Pallikaranai Chennai, Tamil Nadu, India Pincode: 600100 Mobile: 9600027135 E-mail: biswajit@niot.res.in |
Country | India |
Presentation | Oral |
Abstract | The upper layer heat content in the ocean plays a crucial role in cyclone formation and movement Cyclone. The network of deep sea instrumented moored buoy systems deployed in Northern Indian Ocean by National Institute of Ocean Technology(NIOT) provides high density in-situ data which consist of meteorological and oceanographic variables along with temperature and salinity profile measurements in north Indian Ocean used for validation of forecasting. This network of buoys collects marine data in real-time for climate studies, cyclone forecast and warning applications. To improve the accuracy of cyclone forecasting, a unique algorithm is implemented in this indigenous buoy system capable of transmitting real time data sets in high frequency mode during cyclone at low pressure and high wind speeds. One of the Indian moored buoy system BD13 (87E, 14 N) deployed in Northern Bay of Bengal was very close to the cyclone track at a distance of 74 km (40 nm) had switched over to high frequency transmission mode during the passage of cyclone Amphan on 19th May 2020. All the OMNI buoy systems are deployed with inverse catenary mooring, with the combination of inductive cable, nylon rope polypropylene and long link chains with the scope of 1.2 to 1.4 to withstand the buoy from the severe cyclonic storm but at the same time it will be highly respond to wind, wave, and current forcing especially during cyclone which will lead to deviation in subsurface temperature measurements. The standard sensor fit of the OMNI buoy systems has the sea surface temperature sensor varying from 1 m to 500 m at discrete depths of 1, 5, 10, 15, 20, 30, 50, 75, 100, 200, and 500 m. The sensor fixed at a depth of 500 m has the additional pressure parameter to ensure the depth of measurement. Various studies have been shown that, the upper ocean mixing and temperate cooling during the passage of cyclone is high but this study reveals that the measuring sensors vertical movement in the deeper depth is more than the surface sensors vertical movement during the cyclonic period has the buoy experiencing the extreme weather condition. A max depth variation of 80 m has been observed at 500 m during the cyclone Amphan. The depth variation of the other sensor has been analyzed in orcaflex software by using the mooring design data and forcing by the environmental parameter. A temperature deviation field has been calculated by subtracting original temperature from the interpolated temperature at original deployed depth. The study shows that the maximum value of temperature deviation in the lowest instrumented depth where the line experiences a greater range of motion. |