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Observed Thermal Inversions and Associated Oceanographic Features in the Coastal Waters off North East Coast of India


Affiliations
1 Naval Physical and Oceanographic Laboratory (NPOL), Thrikkakara, Cochin-682 021, India
2 DHI-NTU Research Centre, DHI Water and Environment, 200, Pandan Loop, Pantech-21, Singapore 128388, Singapore
3 Cochin University of Science & Technology (CUSAT), Kochi-682 016, India
     

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During one of the ongoing scientific missions in December 2000 off Paradeep, north-east coast of India various oceanographic and meteorological observations were made from a time-series location beside the selected spatial locations. The measurements off Paradeep revealed that the tidal effect was very prominent in the coastal region with significant changes in the flow pattern, variations in temperature, salinity and sound speed both in space and time. One of the most important features observed during the experiment was the temperature inversion of 1.5 to 4°C which was consistently present throughout the time-series as well as spatial observations. Generally, such inversions are not observed in other parts of the World Oceans. Measured currents clearly indicated the tidal reversals and spatial variations in the flow pattern. The salinity gradually increased from the coast to deep waters (i.e. about 22 PSU to 32 PSU) within a distance of 60 miles. Winds were low varying between 2 to 5 m/s and the predominant wind direction during the observation period was north-east. The sea-state generally remained calm with wave height varying between 0.2 and 0.6m (fair weather season). Tidal influence up to a depth of 50m appeared to be very prominent with its semidiurnal reversal both in magnitude as well as direction. Current speed varied between 0.1 m/s to 0.6 m/s and the predominant direction near to coast was south-west. The inversion layer moved from the surface towards deeper waters during the time-series observations. This might be due to the changes in tidal circulation pattern during the lunar cycle. The measurements during this scientific mission also suggested a salinity front in the upper layers which was extending from the coast up to 40 km offshore.

Keywords

Thermal Inversion, Tidal Reversal, Nearshore Hydrodynamics, Measurements off Paradeep, Observations North-east Coast of India.
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  • Observed Thermal Inversions and Associated Oceanographic Features in the Coastal Waters off North East Coast of India

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Authors

J. Swain
Naval Physical and Oceanographic Laboratory (NPOL), Thrikkakara, Cochin-682 021, India
P. A. Umesh
Naval Physical and Oceanographic Laboratory (NPOL), Thrikkakara, Cochin-682 021, India
J. K. Panigrahi
DHI-NTU Research Centre, DHI Water and Environment, 200, Pandan Loop, Pantech-21, Singapore 128388, Singapore
A. N. Balchand
Cochin University of Science & Technology (CUSAT), Kochi-682 016, India

Abstract


During one of the ongoing scientific missions in December 2000 off Paradeep, north-east coast of India various oceanographic and meteorological observations were made from a time-series location beside the selected spatial locations. The measurements off Paradeep revealed that the tidal effect was very prominent in the coastal region with significant changes in the flow pattern, variations in temperature, salinity and sound speed both in space and time. One of the most important features observed during the experiment was the temperature inversion of 1.5 to 4°C which was consistently present throughout the time-series as well as spatial observations. Generally, such inversions are not observed in other parts of the World Oceans. Measured currents clearly indicated the tidal reversals and spatial variations in the flow pattern. The salinity gradually increased from the coast to deep waters (i.e. about 22 PSU to 32 PSU) within a distance of 60 miles. Winds were low varying between 2 to 5 m/s and the predominant wind direction during the observation period was north-east. The sea-state generally remained calm with wave height varying between 0.2 and 0.6m (fair weather season). Tidal influence up to a depth of 50m appeared to be very prominent with its semidiurnal reversal both in magnitude as well as direction. Current speed varied between 0.1 m/s to 0.6 m/s and the predominant direction near to coast was south-west. The inversion layer moved from the surface towards deeper waters during the time-series observations. This might be due to the changes in tidal circulation pattern during the lunar cycle. The measurements during this scientific mission also suggested a salinity front in the upper layers which was extending from the coast up to 40 km offshore.

Keywords


Thermal Inversion, Tidal Reversal, Nearshore Hydrodynamics, Measurements off Paradeep, Observations North-east Coast of India.

References